diff --git a/calculatorpp/AndroidManifest.xml b/calculatorpp/AndroidManifest.xml
index 03991aca..d983d46b 100644
--- a/calculatorpp/AndroidManifest.xml
+++ b/calculatorpp/AndroidManifest.xml
@@ -1,66 +1,66 @@
-<?xml version="1.0" encoding="utf-8"?>
-<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:installLocation="auto" android:versionCode="81" android:versionName="1.3.2"
-          package="org.solovyev.android.calculator">
-
-    <uses-permission android:name="android.permission.VIBRATE"/>
-    <uses-permission android:name="android.permission.INTERNET"/>
-    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
-    <uses-permission android:name="com.android.vending.BILLING"/>
-
-    <uses-sdk android:minSdkVersion="4" android:targetSdkVersion="8"/>
-
-    <application android:debuggable="true" android:hardwareAccelerated="false" android:icon="@drawable/icon" android:label="@string/c_app_name" android:name=".CalculatorApplication" android:theme="@style/metro_blue_theme">
-
-        <activity android:label="@string/c_app_name" android:name=".CalculatorActivity" android:windowSoftInputMode="adjustPan">
-
-            <intent-filter>
-                <action android:name="android.intent.action.MAIN"/>
-                <category android:name="android.intent.category.LAUNCHER"/>
-            </intent-filter>
-
-        </activity>
-
-        <!--NOTE: a:configChanges="orientation|keyboardHidden" is needed to correct work of dialog windows (not to close them on orientation change) -->
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_app_settings" android:name=".CalculatorPreferencesActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_history" android:name=".history.CalculatorHistoryFragmentActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_about" android:name=".about.CalculatorAboutTabActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_about" android:name=".about.CalculatorAboutActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_about" android:name=".about.CalculatorReleaseNotesActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_help" android:name=".help.CalculatorHelpTabActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_help" android:name=".help.HelpFaqActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_help" android:name=".help.HelpHintsActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_help" android:name=".help.HelpScreensActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_functions" android:name=".math.edit.CalculatorFunctionsTabActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_functions" android:name=".math.edit.CalculatorFunctionsActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_operators" android:name=".math.edit.CalculatorOperatorsActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_vars_and_constants" android:name=".math.edit.CalculatorVarsTabActivity"/>
-
-        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_vars_and_constants" android:name=".math.edit.CalculatorVarsActivity"/>
-
-        <activity android:label="@string/c_plot_graph" android:name=".plot.CalculatorPlotActivity"/>
-
-        <activity android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize" android:name="com.google.ads.AdActivity"/>
-
-        <service android:name="net.robotmedia.billing.BillingService"/>
-        <receiver android:name="net.robotmedia.billing.BillingReceiver">
-            <intent-filter>
-                <action android:name="com.android.vending.billing.IN_APP_NOTIFY"/>
-                <action android:name="com.android.vending.billing.RESPONSE_CODE"/>
-                <action android:name="com.android.vending.billing.PURCHASE_STATE_CHANGED"/>
-            </intent-filter>
-        </receiver>
-
-    </application>
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:installLocation="auto" android:versionCode="81" android:versionName="1.3.2"
+          package="org.solovyev.android.calculator">
+
+    <uses-permission android:name="android.permission.VIBRATE"/>
+    <uses-permission android:name="android.permission.INTERNET"/>
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
+    <uses-permission android:name="com.android.vending.BILLING"/>
+
+    <uses-sdk android:minSdkVersion="4" android:targetSdkVersion="8"/>
+
+    <application android:debuggable="true" android:hardwareAccelerated="false" android:icon="@drawable/icon" android:label="@string/c_app_name" android:name=".CalculatorApplication" android:theme="@style/metro_blue_theme">
+
+        <activity android:label="@string/c_app_name" android:name=".CalculatorActivity" android:windowSoftInputMode="adjustPan">
+
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+
+        </activity>
+
+        <!--NOTE: a:configChanges="orientation|keyboardHidden" is needed to correct work of dialog windows (not to close them on orientation change) -->
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_app_settings" android:name=".CalculatorPreferencesActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_history" android:name=".history.CalculatorHistoryFragmentActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_about" android:name=".about.CalculatorAboutTabActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_about" android:name=".about.CalculatorAboutActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_about" android:name=".about.CalculatorReleaseNotesActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_help" android:name=".help.CalculatorHelpTabActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_help" android:name=".help.HelpFaqActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_help" android:name=".help.HelpHintsActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_help" android:name=".help.HelpScreensActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_functions" android:name=".math.edit.CalculatorFunctionsFragmentActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_functions" android:name=".math.edit.CalculatorFunctionsActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_operators" android:name=".math.edit.CalculatorOperatorsActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_vars_and_constants" android:name=".math.edit.CalculatorVarsFragmentActivity"/>
+
+        <activity android:configChanges="orientation|keyboardHidden" android:label="@string/c_vars_and_constants" android:name=".math.edit.CalculatorVarsFragment"/>
+
+        <activity android:label="@string/c_plot_graph" android:name=".plot.CalculatorPlotActivity"/>
+
+        <activity android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize" android:name="com.google.ads.AdActivity"/>
+
+        <service android:name="net.robotmedia.billing.BillingService"/>
+        <receiver android:name="net.robotmedia.billing.BillingReceiver">
+            <intent-filter>
+                <action android:name="com.android.vending.billing.IN_APP_NOTIFY"/>
+                <action android:name="com.android.vending.billing.RESPONSE_CODE"/>
+                <action android:name="com.android.vending.billing.PURCHASE_STATE_CHANGED"/>
+            </intent-filter>
+        </receiver>
+
+    </application>
 </manifest>
\ No newline at end of file
diff --git a/calculatorpp/res/layout/history_fragment.xml b/calculatorpp/res/layout/history_fragment.xml
index 52a7b89c..b90e45e3 100644
--- a/calculatorpp/res/layout/history_fragment.xml
+++ b/calculatorpp/res/layout/history_fragment.xml
@@ -1,24 +1,17 @@
 <?xml version="1.0" encoding="utf-8"?>
 
 <LinearLayout xmlns:a="http://schemas.android.com/apk/res/android"
-              a:layout_width="match_parent"
-              a:layout_height="match_parent"
+              a:orientation="vertical"
+              a:id="@+id/ad_parent_view"
               style="?fragmentLayoutStyle"
-              a:orientation="vertical">
+              a:layout_width="match_parent"
+              a:layout_height="match_parent">
 
     <TextView a:id="@+id/fragmentTitle"
               a:layout_height="wrap_content"
               a:layout_width="match_parent"
               style="?fragmentTitleStyle"/>
 
-    <include layout="@layout/ad"/>
-
-    <ListView
-            a:layout_width="match_parent"
-            a:layout_height="match_parent"
-            a:id="@android:id/list"
-            a:divider="@null"
-            a:dividerHeight="0dp"
-            a:cacheColorHint="@android:color/transparent"/>
+    <ListView style="?fragmentListViewStyle"/>
 
 </LinearLayout>
\ No newline at end of file
diff --git a/calculatorpp/res/layout/vars.xml b/calculatorpp/res/layout/vars_fragment.xml
similarity index 52%
rename from calculatorpp/res/layout/vars.xml
rename to calculatorpp/res/layout/vars_fragment.xml
index d334aa5a..dd81b2ce 100644
--- a/calculatorpp/res/layout/vars.xml
+++ b/calculatorpp/res/layout/vars_fragment.xml
@@ -9,21 +9,24 @@
 <LinearLayout xmlns:a="http://schemas.android.com/apk/res/android"
     a:orientation="vertical"
 	a:id="@+id/ad_parent_view"
-    a:layout_width="fill_parent"
-    a:layout_height="fill_parent">
+    style="?fragmentLayoutStyle"
+    a:layout_width="match_parent"
+    a:layout_height="match_parent">
 
-    <ListView
-        a:layout_width="fill_parent"
-        a:layout_height="fill_parent"
-        a:layout_weight="1"
-        a:id="@android:id/list"/>
+    <TextView a:id="@+id/fragmentTitle"
+              a:layout_height="wrap_content"
+              a:layout_width="match_parent"
+              style="?fragmentTitleStyle"/>
 
-    <Button
+    <ListView style="?fragmentListViewStyle"/>
+
+    <!-- todo serso: uncomment button-->
+<!--    <Button
         a:layout_width="wrap_content"
         a:layout_height="wrap_content"
         a:layout_gravity="center_horizontal"
         a:text="@string/c_add"
-		style="@style/add_var_button"
-        a:onClick="addVarButtonClickHandler"/>
+		style="?buttonStyle"
+        a:onClick="addVarButtonClickHandler"/>-->
 
 </LinearLayout>
\ No newline at end of file
diff --git a/calculatorpp/res/values/attributes.xml b/calculatorpp/res/values/attributes.xml
index f73b4c14..da21f92c 100644
--- a/calculatorpp/res/values/attributes.xml
+++ b/calculatorpp/res/values/attributes.xml
@@ -8,5 +8,7 @@
 	<attr name="fragmentLayoutStyle" format="reference" />
 	<attr name="secondPaneStyle" format="reference" />
 	<attr name="fragmentTitleStyle" format="reference" />
+	<attr name="fragmentListViewStyle" format="reference" />
+	<attr name="buttonStyle" format="reference" />
 
 </resources>
diff --git a/calculatorpp/res/values/styles-default-theme.xml b/calculatorpp/res/values/styles-default-theme.xml
index 8360bb59..81789ec6 100644
--- a/calculatorpp/res/values/styles-default-theme.xml
+++ b/calculatorpp/res/values/styles-default-theme.xml
@@ -25,9 +25,24 @@
         <item name="android:layout_margin">5dp</item>
     </style>
 
+    <style name="default_fragment_list_view_style">
+         <item name="android:id">@android:id/list</item>
+         <item name="android:divider">@null</item>
+         <item name="android:dividerHeight">0dp</item>
+         <item name="android:cacheColorHint">@android:color/transparent</item>
+         <item name="android:layout_height">match_parent</item>
+         <item name="android:layout_width">match_parent</item>
+         <item name="android:layout_weight">1</item>
+    </style>
+
     <style name="default_fragment_title_style">
         <item name="android:textColor">@android:color/white</item>
         <item name="android:textSize">25sp</item>
+        <item name="android:layout_marginLeft">6dp</item>
+    </style>
+
+    <style name="default_button_style" parent="button_style">
+        <item name="android:background">@drawable/metro_button_blue</item>
     </style>
 
     <style name="default_fragment_layout_style">
@@ -45,5 +60,7 @@
 		<item name="fragmentLayoutStyle">@style/default_fragment_layout_style</item>
 		<item name="secondPaneStyle">@style/default_second_pane_style</item>
 		<item name="fragmentTitleStyle">@style/default_fragment_title_style</item>
+		<item name="fragmentListViewStyle">@style/default_fragment_list_view_style</item>
+		<item name="buttonStyle">@style/default_button_style</item>
 	</style>
 </resources>
\ No newline at end of file
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorActivity.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorActivity.java
index a1e4779e..2f0a679d 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorActivity.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorActivity.java
@@ -15,8 +15,9 @@ import android.preference.PreferenceManager;
 import android.text.Html;
 import android.text.method.LinkMovementMethod;
 import android.util.Log;
-import android.util.TypedValue;
-import android.view.*;
+import android.view.KeyEvent;
+import android.view.LayoutInflater;
+import android.view.View;
 import android.widget.TextView;
 import com.actionbarsherlock.app.SherlockFragmentActivity;
 import net.robotmedia.billing.BillingController;
@@ -28,6 +29,8 @@ import org.solovyev.android.FontSizeAdjuster;
 import org.solovyev.android.calculator.about.CalculatorReleaseNotesActivity;
 import org.solovyev.android.calculator.history.CalculatorHistoryFragment;
 import org.solovyev.android.calculator.history.CalculatorSavedHistoryFragment;
+import org.solovyev.android.calculator.math.edit.CalculatorVarsFragment;
+import org.solovyev.android.calculator.model.VarCategory;
 import org.solovyev.android.fragments.FragmentUtils;
 import org.solovyev.android.prefs.Preference;
 import org.solovyev.android.view.ColorButton;
@@ -74,6 +77,10 @@ public class CalculatorActivity extends SherlockFragmentActivity implements Font
         if (findViewById(R.id.main_second_pane) != null) {
             activityHelper.addTab(this, "history", CalculatorHistoryFragment.class, null, R.string.c_history, R.id.main_second_pane);
             activityHelper.addTab(this, "saved_history", CalculatorSavedHistoryFragment.class, null, R.string.c_saved_history, R.id.main_second_pane);
+
+            for (VarCategory category : VarCategory.getCategoriesByTabOrder()) {
+                activityHelper.addTab(this, "vars_" + category.name(), CalculatorVarsFragment.class, CalculatorVarsFragment.createBundleFor(category.name()), category.getCaptionId(), R.id.main_second_pane);
+            }
             activityHelper.restoreSavedTab(this);
         }
 
@@ -211,11 +218,11 @@ public class CalculatorActivity extends SherlockFragmentActivity implements Font
 	 */
 	@Override
 	public void adjustFontSize(@NotNull TextView view) {
-		float fontPixelSize = view.getTextSize();
+		/*float fontPixelSize = view.getTextSize();
 		Display display = getWindowManager().getDefaultDisplay();
 		int h = Math.min(display.getWidth(), display.getHeight());
 		float ratio = (float) h / HVGA_WIDTH_PIXELS;
-		view.setTextSize(TypedValue.COMPLEX_UNIT_PX, fontPixelSize * ratio);
+		view.setTextSize(TypedValue.COMPLEX_UNIT_PX, fontPixelSize * ratio);*/
 	}
 
     @Override
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorActivityLauncher.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorActivityLauncher.java
index c68e7547..58feff03 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorActivityLauncher.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorActivityLauncher.java
@@ -10,10 +10,10 @@ import org.jetbrains.annotations.NotNull;
 import org.solovyev.android.calculator.about.CalculatorAboutTabActivity;
 import org.solovyev.android.calculator.help.CalculatorHelpTabActivity;
 import org.solovyev.android.calculator.history.CalculatorHistoryFragmentActivity;
-import org.solovyev.android.calculator.math.edit.CalculatorFunctionsTabActivity;
+import org.solovyev.android.calculator.math.edit.CalculatorFunctionsFragmentActivity;
 import org.solovyev.android.calculator.math.edit.CalculatorOperatorsActivity;
-import org.solovyev.android.calculator.math.edit.CalculatorVarsTabActivity;
-import org.solovyev.android.calculator.math.edit.CalculatorVarsActivity;
+import org.solovyev.android.calculator.math.edit.CalculatorVarsFragment;
+import org.solovyev.android.calculator.math.edit.CalculatorVarsFragmentActivity;
 import org.solovyev.android.calculator.plot.CalculatorPlotActivity;
 import org.solovyev.common.text.StringUtils;
 
@@ -41,7 +41,7 @@ public class CalculatorActivityLauncher {
 	}
 
 	public static void showFunctions(@NotNull final Context context) {
-		context.startActivity(new Intent(context, CalculatorFunctionsTabActivity.class));
+		context.startActivity(new Intent(context, CalculatorFunctionsFragmentActivity.class));
 	}
 
 	public static void showOperators(@NotNull final Context context) {
@@ -49,7 +49,7 @@ public class CalculatorActivityLauncher {
 	}
 
 	public static void showVars(@NotNull final Context context) {
-		context.startActivity(new Intent(context, CalculatorVarsTabActivity.class));
+		context.startActivity(new Intent(context, CalculatorVarsFragmentActivity.class));
 	}
 
 	public static void plotGraph(@NotNull final Context context, @NotNull Generic generic, @NotNull Constant constant){
@@ -65,9 +65,9 @@ public class CalculatorActivityLauncher {
         if (viewState.isValid() ) {
 			final String varValue = viewState.getText();
 			if (!StringUtils.isEmpty(varValue)) {
-				if (CalculatorVarsActivity.isValidValue(varValue)) {
-					final Intent intent = new Intent(context, CalculatorVarsTabActivity.class);
-					intent.putExtra(CalculatorVarsActivity.CREATE_VAR_EXTRA_STRING, varValue);
+				if (CalculatorVarsFragment.isValidValue(varValue)) {
+					final Intent intent = new Intent(context, CalculatorVarsFragmentActivity.class);
+					intent.putExtra(CalculatorVarsFragment.CREATE_VAR_EXTRA_STRING, varValue);
 					context.startActivity(intent);
 				} else {
 					Toast.makeText(context, R.string.c_not_valid_result, Toast.LENGTH_SHORT).show();
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorFragmentHelper.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorFragmentHelper.java
index 2cf9e12b..c7e6cd42 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorFragmentHelper.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorFragmentHelper.java
@@ -11,4 +11,6 @@ import org.jetbrains.annotations.NotNull;
 public interface CalculatorFragmentHelper {
 
     boolean isPane(@NotNull Fragment fragment);
+
+    void setPaneTitle(@NotNull Fragment fragment, int titleResId);
 }
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorFragmentHelperImpl.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorFragmentHelperImpl.java
index 5a716f6d..1caaf374 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorFragmentHelperImpl.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/CalculatorFragmentHelperImpl.java
@@ -1,6 +1,8 @@
 package org.solovyev.android.calculator;
 
 import android.support.v4.app.Fragment;
+import android.view.View;
+import android.widget.TextView;
 import org.jetbrains.annotations.NotNull;
 
 /**
@@ -14,4 +16,13 @@ public class CalculatorFragmentHelperImpl implements CalculatorFragmentHelper {
     public boolean isPane(@NotNull Fragment fragment) {
         return fragment.getActivity() instanceof CalculatorActivity;
     }
+
+    public void setPaneTitle(@NotNull Fragment fragment, int titleResId) {
+        final TextView fragmentTitle = (TextView) fragment.getView().findViewById(R.id.fragmentTitle);
+        if (!isPane(fragment)) {
+            fragmentTitle.setVisibility(View.GONE);
+        } else {
+            fragmentTitle.setText(fragment.getString(titleResId).toUpperCase());
+        }
+    }
 }
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/history/AbstractCalculatorHistoryFragment.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/history/AbstractCalculatorHistoryFragment.java
index 4c81732a..033eb608 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/history/AbstractCalculatorHistoryFragment.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/history/AbstractCalculatorHistoryFragment.java
@@ -15,7 +15,6 @@ import android.view.ViewGroup;
 import android.widget.AdapterView;
 import android.widget.ArrayAdapter;
 import android.widget.ListView;
-import android.widget.TextView;
 import com.actionbarsherlock.app.SherlockListFragment;
 import com.google.ads.AdView;
 import org.jetbrains.annotations.NotNull;
@@ -114,12 +113,7 @@ public abstract class AbstractCalculatorHistoryFragment extends SherlockListFrag
 
         logDebug("onViewCreated");
 
-        final TextView fragmentTitle = (TextView) view.findViewById(R.id.fragmentTitle);
-        if (!fragmentHelper.isPane(this)) {
-            fragmentTitle.setVisibility(View.GONE);
-        } else {
-            fragmentTitle.setText(this.getString(getFragmentTitleResId()).toUpperCase());
-        }
+        fragmentHelper.setPaneTitle(this, getTitleResId());
 
         adapter = new HistoryArrayAdapter(this.getActivity(), getItemLayoutId(), R.id.history_item, new ArrayList<CalculatorHistoryState>());
         setListAdapter(adapter);
@@ -172,7 +166,7 @@ public abstract class AbstractCalculatorHistoryFragment extends SherlockListFrag
         adView = AdsController.getInstance().inflateAd(this.getActivity(), (ViewGroup)view.findViewById(R.id.ad_parent_view), R.id.ad_parent_view);
     }
 
-    protected abstract int getFragmentTitleResId();
+    protected abstract int getTitleResId();
 
     @Override
 	public void onDestroy() {
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/history/CalculatorHistoryFragment.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/history/CalculatorHistoryFragment.java
index 5f0d3274..f80be9a3 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/history/CalculatorHistoryFragment.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/history/CalculatorHistoryFragment.java
@@ -21,7 +21,7 @@ import java.util.List;
 public class CalculatorHistoryFragment extends AbstractCalculatorHistoryFragment {
 
     @Override
-    protected int getFragmentTitleResId() {
+    protected int getTitleResId() {
         return R.string.c_history;
     }
 
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/history/CalculatorSavedHistoryFragment.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/history/CalculatorSavedHistoryFragment.java
index 700680e1..766de564 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/history/CalculatorSavedHistoryFragment.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/history/CalculatorSavedHistoryFragment.java
@@ -21,7 +21,7 @@ import java.util.List;
 public class CalculatorSavedHistoryFragment extends AbstractCalculatorHistoryFragment {
 
     @Override
-    protected int getFragmentTitleResId() {
+    protected int getTitleResId() {
         return R.string.c_saved_history;
     }
 
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/AbstractMathEntityListActivity.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/AbstractMathEntityListFragment.java
similarity index 70%
rename from calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/AbstractMathEntityListActivity.java
rename to calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/AbstractMathEntityListFragment.java
index 36b414f9..05bd214f 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/AbstractMathEntityListActivity.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/AbstractMathEntityListFragment.java
@@ -7,7 +7,6 @@
 package org.solovyev.android.calculator.math.edit;
 
 import android.app.Activity;
-import android.app.ListActivity;
 import android.content.Context;
 import android.content.Intent;
 import android.os.Bundle;
@@ -15,19 +14,18 @@ import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.*;
+import com.actionbarsherlock.app.SherlockListFragment;
 import com.google.ads.AdView;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.solovyev.android.ads.AdsController;
-import org.solovyev.android.calculator.CalculatorLocatorImpl;
-import org.solovyev.android.calculator.R;
-import org.solovyev.android.calculator.CalculatorMathRegistry;
+import org.solovyev.android.calculator.*;
 import org.solovyev.android.menu.AMenuBuilder;
 import org.solovyev.android.menu.LabeledMenuItem;
 import org.solovyev.android.menu.MenuImpl;
 import org.solovyev.common.equals.EqualsTool;
-import org.solovyev.common.filter.FilterRule;
 import org.solovyev.common.filter.Filter;
+import org.solovyev.common.filter.FilterRule;
 import org.solovyev.common.math.MathEntity;
 import org.solovyev.common.text.StringUtils;
 
@@ -40,12 +38,29 @@ import java.util.List;
  * Date: 12/21/11
  * Time: 9:24 PM
  */
-public abstract class AbstractMathEntityListActivity<T extends MathEntity> extends ListActivity {
+public abstract class AbstractMathEntityListFragment<T extends MathEntity> extends SherlockListFragment {
+
+    /*
+    **********************************************************************
+    *
+    *                           CONSTANTS
+    *
+    **********************************************************************
+    */
 
     public static final String MATH_ENTITY_CATEGORY_EXTRA_STRING = "org.solovyev.android.calculator.CalculatorVarsActivity_math_entity_category";
 
 	protected final static List<Character> acceptableChars = Arrays.asList(StringUtils.toObject("1234567890abcdefghijklmnopqrstuvwxyzйцукенгшщзхъфывапролджэячсмитьбюё_".toCharArray()));
 
+
+    /*
+    **********************************************************************
+    *
+    *                           FIELDS
+    *
+    **********************************************************************
+    */
+
     @Nullable
     private MathEntityArrayAdapter<T> adapter;
     
@@ -55,47 +70,35 @@ public abstract class AbstractMathEntityListActivity<T extends MathEntity> exten
 	@Nullable
 	private AdView adView;
 
-	static void createTab(@NotNull Context context,
-                          @NotNull TabHost tabHost,
-                          @NotNull String tabId,
-                          @NotNull String categoryId,
-                          int tabCaptionId,
-                          @NotNull Class<? extends Activity> activityClass,
-                          @Nullable Intent parentIntent) {
+    @NotNull
+    private CalculatorFragmentHelper fragmentHelper = CalculatorApplication.getInstance().createFragmentHelper();
 
-        TabHost.TabSpec spec;
 
-        final Intent intent;
-        if (parentIntent != null) {
-            intent = new Intent(parentIntent);
-        } else {
-            intent = new Intent();
-        }
-        intent.setClass(context, activityClass);
-        intent.putExtra(MATH_ENTITY_CATEGORY_EXTRA_STRING, categoryId);
-
-        // Initialize a TabSpec for each tab and add it to the TabHost
-        spec = tabHost.newTabSpec(tabId).setIndicator(context.getString(tabCaptionId)).setContent(intent);
-
-        tabHost.addTab(spec);
-    }
-
-    protected int getLayoutId() {
+    protected int getLayoutResId() {
         return R.layout.math_entities;
     }
 
+
     @Override
-    protected void onCreate(Bundle savedInstanceState) {
+    public void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
 
-        setContentView(getLayoutId());
-
-		adView = AdsController.getInstance().inflateAd(this);
-
-		final Intent intent = getIntent();
-        if ( intent != null ) {
-            category = intent.getStringExtra(MATH_ENTITY_CATEGORY_EXTRA_STRING);
+        final Bundle bundle = getArguments();
+        if ( bundle != null ) {
+            category = bundle.getString(MATH_ENTITY_CATEGORY_EXTRA_STRING);
         }
+	}
+
+    @Override
+    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
+        return inflater.inflate(getLayoutResId(), container, false);
+    }
+
+    @Override
+    public void onViewCreated(View view, Bundle savedInstanceState) {
+        super.onViewCreated(view, savedInstanceState);
+
+        this.fragmentHelper.setPaneTitle(this, getTitleResId());
 
         final ListView lv = getListView();
         lv.setTextFilterEnabled(true);
@@ -107,30 +110,32 @@ public abstract class AbstractMathEntityListActivity<T extends MathEntity> exten
                                     final long id) {
 
                 CalculatorLocatorImpl.getInstance().getKeyboard().digitButtonPressed(((MathEntity) parent.getItemAtPosition(position)).getName());
-
-                AbstractMathEntityListActivity.this.finish();
             }
         });
 
-		getListView().setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
-			@Override
-			public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
-				final T item = (T) parent.getItemAtPosition(position);
+        getListView().setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
+            @Override
+            public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
+                final T item = (T) parent.getItemAtPosition(position);
 
-				final List<LabeledMenuItem<T>> menuItems = getMenuItemsOnLongClick(item);
+                final List<LabeledMenuItem<T>> menuItems = getMenuItemsOnLongClick(item);
 
-				if (!menuItems.isEmpty()) {
-					final AMenuBuilder<LabeledMenuItem<T>, T> menuBuilder = AMenuBuilder.newInstance(AbstractMathEntityListActivity.this, MenuImpl.newInstance(menuItems));
-					menuBuilder.create(item).show();
-				}
+                if (!menuItems.isEmpty()) {
+                    final AMenuBuilder<LabeledMenuItem<T>, T> menuBuilder = AMenuBuilder.newInstance(AbstractMathEntityListFragment.this.getActivity(), MenuImpl.newInstance(menuItems));
+                    menuBuilder.create(item).show();
+                }
 
-				return true;
-			}
-		});
-	}
+                return true;
+            }
+        });
 
-	@Override
-	protected void onDestroy() {
+        adView = AdsController.getInstance().inflateAd(this.getActivity(), (ViewGroup)view.findViewById(R.id.ad_parent_view), R.id.ad_parent_view);
+    }
+
+    protected abstract int getTitleResId();
+
+    @Override
+    public void onDestroy() {
 		if (this.adView != null) {
 			this.adView.destroy();
 		}
@@ -141,10 +146,10 @@ public abstract class AbstractMathEntityListActivity<T extends MathEntity> exten
 	protected abstract List<LabeledMenuItem<T>> getMenuItemsOnLongClick(@NotNull T item);
 
 	@Override
-    protected void onResume() {
+    public void onResume() {
         super.onResume();
 
-        adapter = new MathEntityArrayAdapter<T>(getDescriptionGetter(), this, R.layout.math_entity, R.id.math_entity_text, getMathEntitiesByCategory());
+        adapter = new MathEntityArrayAdapter<T>(getDescriptionGetter(), this.getActivity(), R.layout.math_entity, R.id.math_entity_text, getMathEntitiesByCategory());
         setListAdapter(adapter);
 
         sort();
@@ -216,7 +221,7 @@ public abstract class AbstractMathEntityListActivity<T extends MathEntity> exten
             if (!StringUtils.isEmpty(mathEntityDescription)) {
                 TextView description = (TextView) result.findViewById(R.id.math_entity_description);
                 if (description == null) {
-                    final LayoutInflater layoutInflater = (LayoutInflater) getContext().getSystemService(LAYOUT_INFLATER_SERVICE);
+                    final LayoutInflater layoutInflater = (LayoutInflater) getContext().getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
                     final ViewGroup itemView = (ViewGroup) layoutInflater.inflate(R.layout.math_entity, null);
                     description = (TextView) itemView.findViewById(R.id.math_entity_description);
                     itemView.removeView(description);
@@ -273,4 +278,44 @@ public abstract class AbstractMathEntityListActivity<T extends MathEntity> exten
 			this.adapter.notifyDataSetChanged();
 		}
 	}
+
+    /*
+    **********************************************************************
+    *
+    *                           STATIC
+    *
+    **********************************************************************
+    */
+
+    static void createTab(@NotNull Context context,
+                          @NotNull TabHost tabHost,
+                          @NotNull String tabId,
+                          @NotNull String categoryId,
+                          int tabCaptionId,
+                          @NotNull Class<? extends Activity> activityClass,
+                          @Nullable Intent parentIntent) {
+
+        TabHost.TabSpec spec;
+
+        final Intent intent;
+        if (parentIntent != null) {
+            intent = new Intent(parentIntent);
+        } else {
+            intent = new Intent();
+        }
+        intent.setClass(context, activityClass);
+        intent.putExtra(MATH_ENTITY_CATEGORY_EXTRA_STRING, categoryId);
+
+        // Initialize a TabSpec for each tab and add it to the TabHost
+        spec = tabHost.newTabSpec(tabId).setIndicator(context.getString(tabCaptionId)).setContent(intent);
+
+        tabHost.addTab(spec);
+    }
+
+    @NotNull
+    public static Bundle createBundleFor(@NotNull String categoryId) {
+        final Bundle result = new Bundle(1);
+        result.putString(MATH_ENTITY_CATEGORY_EXTRA_STRING, categoryId);
+        return result;
+    }
 }
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsActivity.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsActivity.java
index e54705a9..f0fbcd23 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsActivity.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsActivity.java
@@ -26,54 +26,12 @@ import java.util.List;
  * Date: 10/29/11
  * Time: 4:55 PM
  */
-public class CalculatorFunctionsActivity extends AbstractMathEntityListActivity<Function> {
-
-	private static enum LongClickMenuItem implements LabeledMenuItem<Function> {
-		use(R.string.c_use) {
-			@Override
-			public void onClick(@NotNull Function data, @NotNull Context context) {
-                CalculatorLocatorImpl.getInstance().getKeyboard().digitButtonPressed(data.getName());
-				if (context instanceof Activity) {
-					((Activity) context).finish();
-				}
-			}
-		},
-
-		/*edit(R.string.c_edit) {
-			@Override
-			public void doAction(@NotNull Function data, @NotNull Context context) {
-				if (context instanceof AbstractMathEntityListActivity) {
-				}
-			}
-		},*/
-
-		copy_description(R.string.c_copy_description) {
-			@Override
-			public void onClick(@NotNull Function data, @NotNull Context context) {
-				final String text = CalculatorLocatorImpl.getInstance().getEngine().getFunctionsRegistry().getDescription(data.getName());
-				if (!StringUtils.isEmpty(text)) {
-					final ClipboardManager clipboard = (ClipboardManager) context.getSystemService(Activity.CLIPBOARD_SERVICE);
-					clipboard.setText(text);
-				}
-			}
-		};
-		private final int captionId;
-
-		LongClickMenuItem(int captionId) {
-			this.captionId = captionId;
-		}
-
-		@NotNull
-		@Override
-		public String getCaption(@NotNull Context context) {
-			return context.getString(captionId);
-		}
-	}
+public class CalculatorFunctionsActivity extends AbstractMathEntityListFragment<Function> {
 
 	public static final String CREATE_FUN_EXTRA_STRING = "org.solovyev.android.calculator.math.edit.CalculatorFunctionsTabActivity_create_fun";
 
 	@Override
-	protected void onCreate(Bundle savedInstanceState) {
+    public void onCreate(Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
 
 		/*getListView().setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
@@ -104,7 +62,12 @@ public class CalculatorFunctionsActivity extends AbstractMathEntityListActivity<
 		}*/
 	}
 
-	@NotNull
+    @Override
+    protected int getTitleResId() {
+        return R.string.c_functions;
+    }
+
+    @NotNull
 	@Override
 	protected List<LabeledMenuItem<Function>> getMenuItemsOnLongClick(@NotNull Function item) {
 		List<LabeledMenuItem<Function>> result = new ArrayList<LabeledMenuItem<Function>>(Arrays.asList(LongClickMenuItem.values()));
@@ -218,4 +181,54 @@ public class CalculatorFunctionsActivity extends AbstractMathEntityListActivity<
 	protected String getMathEntityCategory(@NotNull Function function) {
 		return CalculatorLocatorImpl.getInstance().getEngine().getFunctionsRegistry().getCategory(function);
 	}
+
+    /*
+    **********************************************************************
+    *
+    *                           STATIC
+    *
+    **********************************************************************
+    */
+
+    private static enum LongClickMenuItem implements LabeledMenuItem<Function> {
+        use(R.string.c_use) {
+            @Override
+            public void onClick(@NotNull Function data, @NotNull Context context) {
+                CalculatorLocatorImpl.getInstance().getKeyboard().digitButtonPressed(data.getName());
+                if (context instanceof Activity) {
+                    ((Activity) context).finish();
+                }
+            }
+        },
+
+        /*edit(R.string.c_edit) {
+              @Override
+              public void doAction(@NotNull Function data, @NotNull Context context) {
+                  if (context instanceof AbstractMathEntityListActivity) {
+                  }
+              }
+          },*/
+
+        copy_description(R.string.c_copy_description) {
+            @Override
+            public void onClick(@NotNull Function data, @NotNull Context context) {
+                final String text = CalculatorLocatorImpl.getInstance().getEngine().getFunctionsRegistry().getDescription(data.getName());
+                if (!StringUtils.isEmpty(text)) {
+                    final ClipboardManager clipboard = (ClipboardManager) context.getSystemService(Activity.CLIPBOARD_SERVICE);
+                    clipboard.setText(text);
+                }
+            }
+        };
+        private final int captionId;
+
+        LongClickMenuItem(int captionId) {
+            this.captionId = captionId;
+        }
+
+        @NotNull
+        @Override
+        public String getCaption(@NotNull Context context) {
+            return context.getString(captionId);
+        }
+    }
 }
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsFragmentActivity.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsFragmentActivity.java
new file mode 100644
index 00000000..745d9f1a
--- /dev/null
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsFragmentActivity.java
@@ -0,0 +1,67 @@
+/*
+ * Copyright (c) 2009-2011. Created by serso aka se.solovyev.
+ * For more information, please, contact se.solovyev@gmail.com
+ * or visit http://se.solovyev.org
+ */
+
+package org.solovyev.android.calculator.math.edit;
+
+import android.os.Bundle;
+import com.actionbarsherlock.app.SherlockFragmentActivity;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.solovyev.android.calculator.*;
+import org.solovyev.android.calculator.history.CalculatorHistoryFragment;
+import org.solovyev.android.calculator.history.CalculatorHistoryFragmentActivity;
+import org.solovyev.android.calculator.model.AndroidFunctionsMathRegistry;
+
+/**
+ * User: serso
+ * Date: 12/21/11
+ * Time: 10:33 PM
+ */
+public class CalculatorFunctionsFragmentActivity extends SherlockFragmentActivity implements CalculatorEventListener {
+
+    @NotNull
+    private final CalculatorActivityHelper activityHelper = CalculatorApplication.getInstance().createActivityHelper(R.layout.main_empty, CalculatorHistoryFragmentActivity.class.getSimpleName());
+
+    @Override
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        activityHelper.onCreate(this, savedInstanceState);
+
+        for (AndroidFunctionsMathRegistry.Category category : AndroidFunctionsMathRegistry.Category.getCategoriesByTabOrder()) {
+            activityHelper.addTab(this, category.name(), CalculatorHistoryFragment.class, null, category.getCaptionId(), R.id.main_layout);
+
+        }
+
+        CalculatorLocatorImpl.getInstance().getCalculator().addCalculatorEventListener(this);
+    }
+
+    @Override
+    protected void onSaveInstanceState(Bundle outState) {
+        super.onSaveInstanceState(outState);
+
+        activityHelper.onSaveInstanceState(this, outState);
+    }
+
+    @Override
+    protected void onResume() {
+        super.onResume();
+
+        activityHelper.onResume(this);
+    }
+
+    @Override
+    protected void onDestroy() {
+        super.onDestroy();
+
+        CalculatorLocatorImpl.getInstance().getCalculator().removeCalculatorEventListener(this);
+    }
+
+    @Override
+    public void onCalculatorEvent(@NotNull CalculatorEventData calculatorEventData, @NotNull CalculatorEventType calculatorEventType, @Nullable Object data) {
+        //To change body of implemented methods use File | Settings | File Templates.
+    }
+}
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsTabActivity.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsTabActivity.java
deleted file mode 100644
index 94913055..00000000
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorFunctionsTabActivity.java
+++ /dev/null
@@ -1,52 +0,0 @@
-/*
- * Copyright (c) 2009-2011. Created by serso aka se.solovyev.
- * For more information, please, contact se.solovyev@gmail.com
- * or visit http://se.solovyev.org
- */
-
-package org.solovyev.android.calculator.math.edit;
-
-import android.app.TabActivity;
-import android.os.Bundle;
-import android.widget.TabHost;
-import org.jetbrains.annotations.Nullable;
-import org.solovyev.android.AndroidUtils;
-import org.solovyev.android.LastTabSaver;
-import org.solovyev.android.calculator.R;
-import org.solovyev.android.calculator.model.AndroidFunctionsMathRegistry;
-
-/**
- * User: serso
- * Date: 12/21/11
- * Time: 10:33 PM
- */
-public class CalculatorFunctionsTabActivity extends TabActivity {
-
-	@Nullable
-	private LastTabSaver lastTabSaver;
-
-    @Override
-    public void onCreate(@Nullable Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-
-        setContentView(R.layout.tabs);
-
-        final TabHost tabHost = getTabHost();
-
-        for (AndroidFunctionsMathRegistry.Category category : AndroidFunctionsMathRegistry.Category.getCategoriesByTabOrder()) {
-            AbstractMathEntityListActivity.createTab(this, tabHost, category.name(), category.name(), category.getCaptionId(), CalculatorFunctionsActivity.class, null);
-        }
-
-		this.lastTabSaver = new LastTabSaver(this, AndroidFunctionsMathRegistry.Category.common.name());
-
-        AndroidUtils.centerAndWrapTabsFor(tabHost);
-    }
-
-	@Override
-	protected void onDestroy() {
-		if (lastTabSaver != null) {
-			this.lastTabSaver.destroy();
-		}
-		super.onDestroy();
-	}
-}
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorOperatorsActivity.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorOperatorsActivity.java
index cafb35ab..e5f5587e 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorOperatorsActivity.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorOperatorsActivity.java
@@ -20,49 +20,19 @@ import java.util.List;
  * Time: 1:53 PM
  */
 
-public class CalculatorOperatorsActivity extends AbstractMathEntityListActivity<Operator> {
+public class CalculatorOperatorsActivity extends AbstractMathEntityListFragment<Operator> {
 
-	private static enum LongClickMenuItem implements LabeledMenuItem<Operator> {
+    @Override
+    protected int getTitleResId() {
+        return R.string.c_operators;
+    }
 
-		use(R.string.c_use) {
-			@Override
-			public void onClick(@NotNull Operator data, @NotNull Context context) {
-                CalculatorLocatorImpl.getInstance().getKeyboard().digitButtonPressed(data.getName());
-				if (context instanceof Activity) {
-					((Activity) context).finish();
-				}
-			}
-		},
-
-		copy_description(R.string.c_copy_description) {
-			@Override
-			public void onClick(@NotNull Operator data, @NotNull Context context) {
-				final String text = OperatorDescriptionGetter.instance.getDescription(context, data.getName());
-				if (!StringUtils.isEmpty(text)) {
-					final ClipboardManager clipboard = (ClipboardManager) context.getSystemService(Activity.CLIPBOARD_SERVICE);
-					clipboard.setText(text);
-				}
-			}
-		};
-		private final int captionId;
-
-		LongClickMenuItem(int captionId) {
-			this.captionId = captionId;
-		}
-
-		@NotNull
-		@Override
-		public String getCaption(@NotNull Context context) {
-			return context.getString(captionId);
-		}
-	}
-
-	@NotNull
+    @NotNull
 	@Override
 	protected List<LabeledMenuItem<Operator>> getMenuItemsOnLongClick(@NotNull Operator item) {
 		final List<LabeledMenuItem<Operator>> result = new ArrayList<LabeledMenuItem<Operator>>(Arrays.asList(LongClickMenuItem.values()));
 
-		if ( StringUtils.isEmpty(OperatorDescriptionGetter.instance.getDescription(this, item.getName())) ) {
+		if ( StringUtils.isEmpty(OperatorDescriptionGetter.instance.getDescription(this.getActivity(), item.getName())) ) {
 			result.remove(LongClickMenuItem.copy_description);
 		}
 
@@ -112,5 +82,48 @@ public class CalculatorOperatorsActivity extends AbstractMathEntityListActivity<
         }
     }
 
+    /*
+    **********************************************************************
+    *
+    *                           STATIC
+    *
+    **********************************************************************
+    */
+
+    private static enum LongClickMenuItem implements LabeledMenuItem<Operator> {
+
+        use(R.string.c_use) {
+            @Override
+            public void onClick(@NotNull Operator data, @NotNull Context context) {
+                CalculatorLocatorImpl.getInstance().getKeyboard().digitButtonPressed(data.getName());
+                if (context instanceof Activity) {
+                    ((Activity) context).finish();
+                }
+            }
+        },
+
+        copy_description(R.string.c_copy_description) {
+            @Override
+            public void onClick(@NotNull Operator data, @NotNull Context context) {
+                final String text = OperatorDescriptionGetter.instance.getDescription(context, data.getName());
+                if (!StringUtils.isEmpty(text)) {
+                    final ClipboardManager clipboard = (ClipboardManager) context.getSystemService(Activity.CLIPBOARD_SERVICE);
+                    clipboard.setText(text);
+                }
+            }
+        };
+        private final int captionId;
+
+        LongClickMenuItem(int captionId) {
+            this.captionId = captionId;
+        }
+
+        @NotNull
+        @Override
+        public String getCaption(@NotNull Context context) {
+            return context.getString(captionId);
+        }
+    }
+
 }
 
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsActivity.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsFragment.java
similarity index 60%
rename from calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsActivity.java
rename to calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsFragment.java
index f680f507..a565b71c 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsActivity.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsFragment.java
@@ -10,12 +10,13 @@ import android.app.Activity;
 import android.app.AlertDialog;
 import android.content.Context;
 import android.content.DialogInterface;
-import android.content.Intent;
 import android.os.Bundle;
+import android.support.v4.app.FragmentActivity;
 import android.text.ClipboardManager;
 import android.text.Editable;
 import android.text.TextWatcher;
-import android.view.*;
+import android.view.LayoutInflater;
+import android.view.View;
 import android.widget.EditText;
 import android.widget.Toast;
 import jscl.math.function.IConstant;
@@ -39,95 +40,37 @@ import java.util.List;
  * Date: 9/28/11
  * Time: 10:55 PM
  */
-public class CalculatorVarsActivity extends AbstractMathEntityListActivity<IConstant> {
-
-	private static enum LongClickMenuItem implements LabeledMenuItem<IConstant>{
-		use(R.string.c_use) {
-			@Override
-			public void onClick(@NotNull IConstant data, @NotNull Context context) {
-                CalculatorLocatorImpl.getInstance().getKeyboard().digitButtonPressed(data.getName());
-				if (context instanceof Activity) {
-					((Activity) context).finish();
-				}
-			}
-		},
-
-		edit(R.string.c_edit) {
-			@Override
-			public void onClick(@NotNull IConstant data, @NotNull Context context) {
-				if (context instanceof AbstractMathEntityListActivity) {
-					createEditVariableDialog((AbstractMathEntityListActivity<IConstant>)context, data, data.getName(), StringUtils.getNotEmpty(data.getValue(), ""), data.getDescription());
-				}
-			}
-		},
-
-		remove(R.string.c_remove) {
-			@Override
-			public void onClick(@NotNull IConstant data, @NotNull Context context) {
-				if (context instanceof AbstractMathEntityListActivity) {
-					new MathEntityRemover<IConstant>(data, null, CalculatorLocatorImpl.getInstance().getEngine().getVarsRegistry(), ((AbstractMathEntityListActivity<IConstant>) context)).showConfirmationDialog();
-				}
-			}
-		},
-
-		copy_value(R.string.c_copy_value) {
-			@Override
-			public void onClick(@NotNull IConstant data, @NotNull Context context) {
-				final String text = data.getValue();
-				if (!StringUtils.isEmpty(text)) {
-					final ClipboardManager clipboard = (ClipboardManager) context.getSystemService(Activity.CLIPBOARD_SERVICE);
-					clipboard.setText(text);
-				}
-			}
-		},
-
-		copy_description(R.string.c_copy_description) {
-			@Override
-			public void onClick(@NotNull IConstant data, @NotNull Context context) {
-				final String text = CalculatorLocatorImpl.getInstance().getEngine().getVarsRegistry().getDescription(data.getName());
-				if (!StringUtils.isEmpty(text)) {
-					final ClipboardManager clipboard = (ClipboardManager) context.getSystemService(Activity.CLIPBOARD_SERVICE);
-					clipboard.setText(text);
-				}
-			}
-		};
-		private final int captionId;
-
-		LongClickMenuItem(int captionId) {
-			this.captionId = captionId;
-		}
-
-		@NotNull
-		@Override
-		public String getCaption(@NotNull Context context) {
-			return context.getString(captionId);
-		}
-	}
+public class CalculatorVarsFragment extends AbstractMathEntityListFragment<IConstant> {
 	
 	public static final String CREATE_VAR_EXTRA_STRING = "org.solovyev.android.calculator.math.edit.CalculatorVarsTabActivity_create_var";
 
 	@Override
-	protected int getLayoutId() {
-		return R.layout.vars;
+	protected int getLayoutResId() {
+		return R.layout.vars_fragment;
 	}
 
 	@Override
-	protected void onCreate(Bundle savedInstanceState) {
+    public void onCreate(Bundle savedInstanceState) {
 		super.onCreate(savedInstanceState);
 
-		final Intent intent = getIntent();
-		if (intent != null) {
-			final String varValue = intent.getStringExtra(CREATE_VAR_EXTRA_STRING);
+		final Bundle bundle = getArguments();
+		if (bundle != null) {
+			final String varValue = bundle.getString(CREATE_VAR_EXTRA_STRING);
 			if (!StringUtils.isEmpty(varValue)) {
 				createEditVariableDialog(this, null, null, varValue, null);
 
 				// in order to stop intent for other tabs
-				intent.removeExtra(CREATE_VAR_EXTRA_STRING);
+                bundle.remove(CREATE_VAR_EXTRA_STRING);
 			}
 		}
 	}
 
-	@NotNull
+    @Override
+    protected int getTitleResId() {
+        return R.string.c_vars;
+    }
+
+    @NotNull
 	@Override
 	protected List<LabeledMenuItem<IConstant>> getMenuItemsOnLongClick(@NotNull IConstant item) {
 		final List<LabeledMenuItem<IConstant>> result = new ArrayList<LabeledMenuItem<IConstant>>(Arrays.asList(LongClickMenuItem.values()));
@@ -179,17 +122,19 @@ public class CalculatorVarsActivity extends AbstractMathEntityListActivity<ICons
 		return CalculatorLocatorImpl.getInstance().getEngine().getVarsRegistry().getCategory(var);
 	}
 
-	private static void createEditVariableDialog(@NotNull final AbstractMathEntityListActivity<IConstant> activity,
+	private static void createEditVariableDialog(@NotNull final AbstractMathEntityListFragment<IConstant> fragment,
 												 @Nullable final IConstant var,
 												 @Nullable final String name,
 												 @Nullable final String value,
 												 @Nullable final String description) {
-		if (var == null || !var.isSystem()) {
+        final FragmentActivity activity = fragment.getActivity();
 
-			final LayoutInflater layoutInflater = (LayoutInflater) activity.getSystemService(LAYOUT_INFLATER_SERVICE);
+        if (var == null || !var.isSystem()) {
+
+			final LayoutInflater layoutInflater = (LayoutInflater) activity.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
 			final View editView = layoutInflater.inflate(R.layout.var_edit, null);
 
-			final String errorMsg = activity.getString(R.string.c_char_is_not_accepted);
+			final String errorMsg = fragment.getString(R.string.c_char_is_not_accepted);
 
 			final EditText editName = (EditText) editView.findViewById(R.id.var_edit_name);
 			editName.setText(name);
@@ -209,7 +154,7 @@ public class CalculatorVarsActivity extends AbstractMathEntityListActivity<ICons
 						char c = s.charAt(i);
 						if (!acceptableChars.contains(c)) {
 							s.delete(i, i + 1);
-							Toast.makeText(activity, String.format(errorMsg, c), Toast.LENGTH_SHORT).show();
+                            Toast.makeText(activity, String.format(errorMsg, c), Toast.LENGTH_SHORT).show();
 						}
 					}
 				}
@@ -233,9 +178,9 @@ public class CalculatorVarsActivity extends AbstractMathEntityListActivity<ICons
 			final AlertDialog.Builder builder = new AlertDialog.Builder(activity)
 					.setCancelable(true)
 					.setNegativeButton(R.string.c_cancel, null)
-					.setPositiveButton(R.string.c_save, new VarEditorSaver<IConstant>(varBuilder, var, editView, activity, CalculatorLocatorImpl.getInstance().getEngine().getVarsRegistry(), new VarEditorSaver.EditorCreator<IConstant>() {
+					.setPositiveButton(R.string.c_save, new VarEditorSaver<IConstant>(varBuilder, var, editView, fragment, CalculatorLocatorImpl.getInstance().getEngine().getVarsRegistry(), new VarEditorSaver.EditorCreator<IConstant>() {
 						@Override
-						public void showEditor(@NotNull AbstractMathEntityListActivity<IConstant> activity, @Nullable IConstant editedInstance, @Nullable String name, @Nullable String value, @Nullable String description) {
+						public void showEditor(@NotNull AbstractMathEntityListFragment<IConstant> activity, @Nullable IConstant editedInstance, @Nullable String name, @Nullable String value, @Nullable String description) {
 							createEditVariableDialog(activity, editedInstance, name, value, description);
 						}
 					}))
@@ -248,9 +193,9 @@ public class CalculatorVarsActivity extends AbstractMathEntityListActivity<ICons
 				builder.setNeutralButton(R.string.c_remove, new MathEntityRemover<IConstant>(var, new DialogInterface.OnClickListener() {
 					@Override
 					public void onClick(DialogInterface dialog, int which) {
-						createEditVariableDialog(activity, var, name, value, description);
+						createEditVariableDialog(fragment, var, name, value, description);
 					}
-				}, CalculatorLocatorImpl.getInstance().getEngine().getVarsRegistry(), activity));
+				}, CalculatorLocatorImpl.getInstance().getEngine().getVarsRegistry(), fragment));
 			} else {
 				// CREATE mode
 
@@ -259,7 +204,7 @@ public class CalculatorVarsActivity extends AbstractMathEntityListActivity<ICons
 
 			builder.create().show();
 		} else {
-			Toast.makeText(activity, activity.getString(R.string.c_sys_var_cannot_be_changed), Toast.LENGTH_LONG).show();
+			Toast.makeText(activity, fragment.getString(R.string.c_sys_var_cannot_be_changed), Toast.LENGTH_LONG).show();
 		}
 	}
 
@@ -268,7 +213,8 @@ public class CalculatorVarsActivity extends AbstractMathEntityListActivity<ICons
 		return true;
 	}
 
-	@Override
+    // todo serso: menu
+/*	@Override
 	public boolean onCreateOptionsMenu(Menu menu) {
 		final MenuInflater menuInflater = getMenuInflater();
 		menuInflater.inflate(R.menu.var_menu, menu);
@@ -289,6 +235,76 @@ public class CalculatorVarsActivity extends AbstractMathEntityListActivity<ICons
 		}
 
 		return result;
-	}
+	}*/
 
+    /*
+    **********************************************************************
+    *
+    *                           STATIC
+    *
+    **********************************************************************
+    */
+
+    private static enum LongClickMenuItem implements LabeledMenuItem<IConstant>{
+        use(R.string.c_use) {
+            @Override
+            public void onClick(@NotNull IConstant data, @NotNull Context context) {
+                CalculatorLocatorImpl.getInstance().getKeyboard().digitButtonPressed(data.getName());
+                if (context instanceof Activity) {
+                    ((Activity) context).finish();
+                }
+            }
+        },
+
+        edit(R.string.c_edit) {
+            @Override
+            public void onClick(@NotNull IConstant data, @NotNull Context context) {
+                /*if (context instanceof AbstractMathEntityListFragment) {
+                    createEditVariableDialog((AbstractMathEntityListFragment<IConstant>)context, data, data.getName(), StringUtils.getNotEmpty(data.getValue(), ""), data.getDescription());
+                }*/
+            }
+        },
+
+        remove(R.string.c_remove) {
+            @Override
+            public void onClick(@NotNull IConstant data, @NotNull Context context) {
+                /*if (context instanceof AbstractMathEntityListFragment) {
+                    new MathEntityRemover<IConstant>(data, null, CalculatorLocatorImpl.getInstance().getEngine().getVarsRegistry(), ((AbstractMathEntityListFragment<IConstant>) context)).showConfirmationDialog();
+                }*/
+            }
+        },
+
+        copy_value(R.string.c_copy_value) {
+            @Override
+            public void onClick(@NotNull IConstant data, @NotNull Context context) {
+                final String text = data.getValue();
+                if (!StringUtils.isEmpty(text)) {
+                    final ClipboardManager clipboard = (ClipboardManager) context.getSystemService(Activity.CLIPBOARD_SERVICE);
+                    clipboard.setText(text);
+                }
+            }
+        },
+
+        copy_description(R.string.c_copy_description) {
+            @Override
+            public void onClick(@NotNull IConstant data, @NotNull Context context) {
+                final String text = CalculatorLocatorImpl.getInstance().getEngine().getVarsRegistry().getDescription(data.getName());
+                if (!StringUtils.isEmpty(text)) {
+                    final ClipboardManager clipboard = (ClipboardManager) context.getSystemService(Activity.CLIPBOARD_SERVICE);
+                    clipboard.setText(text);
+                }
+            }
+        };
+        private final int captionId;
+
+        LongClickMenuItem(int captionId) {
+            this.captionId = captionId;
+        }
+
+        @NotNull
+        @Override
+        public String getCaption(@NotNull Context context) {
+            return context.getString(captionId);
+        }
+    }
 }
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsFragmentActivity.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsFragmentActivity.java
new file mode 100644
index 00000000..ae40c6b2
--- /dev/null
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsFragmentActivity.java
@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2009-2011. Created by serso aka se.solovyev.
+ * For more information, please, contact se.solovyev@gmail.com
+ * or visit http://se.solovyev.org
+ */
+
+package org.solovyev.android.calculator.math.edit;
+
+import android.content.Intent;
+import android.os.Bundle;
+import com.actionbarsherlock.app.SherlockFragmentActivity;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+import org.solovyev.android.calculator.*;
+import org.solovyev.android.calculator.history.CalculatorHistoryFragment;
+import org.solovyev.android.calculator.history.CalculatorHistoryFragmentActivity;
+import org.solovyev.android.calculator.model.VarCategory;
+
+/**
+ * User: serso
+ * Date: 12/21/11
+ * Time: 11:05 PM
+ */
+public class CalculatorVarsFragmentActivity extends SherlockFragmentActivity implements CalculatorEventListener {
+
+    @NotNull
+    private final CalculatorActivityHelper activityHelper = CalculatorApplication.getInstance().createActivityHelper(R.layout.main_empty, CalculatorHistoryFragmentActivity.class.getSimpleName());
+
+    @Override
+    public void onCreate(@Nullable Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+
+        activityHelper.onCreate(this, savedInstanceState);
+
+        final Bundle bundle;
+
+        final Intent intent = getIntent();
+        if (intent != null) {
+            bundle = intent.getExtras();
+        } else {
+            bundle = null;
+        }
+
+        for (VarCategory category : VarCategory.getCategoriesByTabOrder()) {
+            if (category == VarCategory.my) {
+                activityHelper.addTab(this, category.name(), CalculatorHistoryFragment.class, bundle, category.getCaptionId(), R.id.main_layout);
+            } else {
+                activityHelper.addTab(this, category.name(), CalculatorHistoryFragment.class, null, category.getCaptionId(), R.id.main_layout);
+            }
+        }
+
+        CalculatorLocatorImpl.getInstance().getCalculator().addCalculatorEventListener(this);
+    }
+
+    @Override
+    protected void onSaveInstanceState(Bundle outState) {
+        super.onSaveInstanceState(outState);
+
+        activityHelper.onSaveInstanceState(this, outState);
+    }
+
+    @Override
+    protected void onResume() {
+        super.onResume();
+
+        activityHelper.onResume(this);
+    }
+
+    @Override
+    protected void onDestroy() {
+        super.onDestroy();
+
+        CalculatorLocatorImpl.getInstance().getCalculator().removeCalculatorEventListener(this);
+    }
+
+    @Override
+    public void onCalculatorEvent(@NotNull CalculatorEventData calculatorEventData, @NotNull CalculatorEventType calculatorEventType, @Nullable Object data) {
+        //To change body of implemented methods use File | Settings | File Templates.
+    }
+}
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsTabActivity.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsTabActivity.java
deleted file mode 100644
index ce36fdc4..00000000
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/CalculatorVarsTabActivity.java
+++ /dev/null
@@ -1,56 +0,0 @@
-/*
- * Copyright (c) 2009-2011. Created by serso aka se.solovyev.
- * For more information, please, contact se.solovyev@gmail.com
- * or visit http://se.solovyev.org
- */
-
-package org.solovyev.android.calculator.math.edit;
-
-import android.app.TabActivity;
-import android.os.Bundle;
-import android.widget.TabHost;
-import org.jetbrains.annotations.Nullable;
-import org.solovyev.android.AndroidUtils;
-import org.solovyev.android.LastTabSaver;
-import org.solovyev.android.calculator.R;
-import org.solovyev.android.calculator.model.VarCategory;
-
-/**
- * User: serso
- * Date: 12/21/11
- * Time: 11:05 PM
- */
-public class CalculatorVarsTabActivity extends TabActivity {
-
-	@Nullable
-	private LastTabSaver lastTabSaver;
-
-    @Override
-    public void onCreate(@Nullable Bundle savedInstanceState) {
-        super.onCreate(savedInstanceState);
-
-        setContentView(R.layout.tabs);
-
-        final TabHost tabHost = getTabHost();
-
-        for (VarCategory category : VarCategory.getCategoriesByTabOrder()) {
-            if (category == VarCategory.my) {
-                AbstractMathEntityListActivity.createTab(this, tabHost, category.name(), category.name(), category.getCaptionId(), CalculatorVarsActivity.class, getIntent());
-            } else {
-                AbstractMathEntityListActivity.createTab(this, tabHost, category.name(), category.name(), category.getCaptionId(), CalculatorVarsActivity.class, null);
-            }
-        }
-
-		this.lastTabSaver = new LastTabSaver(this, VarCategory.my.name());
-
-        AndroidUtils.centerAndWrapTabsFor(tabHost);
-    }
-
-	@Override
-	protected void onDestroy() {
-		if (lastTabSaver != null) {
-			lastTabSaver.destroy();
-		}
-		super.onDestroy();
-	}
-}
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/FunctionEditorSaver.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/FunctionEditorSaver.java
index 2e65e70b..57564c0b 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/FunctionEditorSaver.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/FunctionEditorSaver.java
@@ -34,7 +34,7 @@ import org.solovyev.common.text.StringUtils;
 public class FunctionEditorSaver implements DialogInterface.OnClickListener{
 
 	public static interface EditorCreator<T extends MathEntity> {
-		void showEditor(@NotNull AbstractMathEntityListActivity<T> activity,
+		void showEditor(@NotNull AbstractMathEntityListFragment<T> activity,
 						@Nullable CustomFunction editedInstance,
 						@Nullable String name,
 						@Nullable String value,
@@ -55,7 +55,7 @@ public class FunctionEditorSaver implements DialogInterface.OnClickListener{
 	private final CalculatorMathRegistry<Function> mathRegistry;
 
 	@NotNull
-	private final AbstractMathEntityListActivity<Function> activity;
+	private final AbstractMathEntityListFragment<Function> fragment;
 
 	@NotNull
 	private View editView;
@@ -63,13 +63,13 @@ public class FunctionEditorSaver implements DialogInterface.OnClickListener{
 	public FunctionEditorSaver(@NotNull MathEntityBuilder<CustomFunction> varBuilder,
 							   @Nullable CustomFunction editedInstance,
 							   @NotNull View editView,
-							   @NotNull AbstractMathEntityListActivity<Function> activity,
+							   @NotNull AbstractMathEntityListFragment<Function> fragment,
 							   @NotNull CalculatorMathRegistry<Function> mathRegistry,
 							   @NotNull EditorCreator<Function> editorCreator) {
 		this.varBuilder = varBuilder;
 		this.editedInstance = editedInstance;
 		this.editView = editView;
-		this.activity = activity;
+		this.fragment = fragment;
 		this.mathRegistry = mathRegistry;
 		this.editorCreator = editorCreator;
 	}
@@ -112,7 +112,7 @@ public class FunctionEditorSaver implements DialogInterface.OnClickListener{
 							error = null;
 						} else {
 							// value is not empty => must be a number
-							boolean valid = CalculatorVarsActivity.isValidValue(value);
+							boolean valid = CalculatorVarsFragment.isValidValue(value);
 
 							if (valid) {
 								varBuilder.setName(name);
@@ -134,21 +134,21 @@ public class FunctionEditorSaver implements DialogInterface.OnClickListener{
 			}
 
 			if (error != null) {
-				Toast.makeText(activity, activity.getString(error), Toast.LENGTH_LONG).show();
-				editorCreator.showEditor(activity, editedInstance, name, value, null, description);
+				Toast.makeText(fragment.getActivity(), fragment.getString(error), Toast.LENGTH_LONG).show();
+				editorCreator.showEditor(fragment, editedInstance, name, value, null, description);
 			} else {
 				final Function addedVar = mathRegistry.add(varBuilder);
-				if (activity.isInCategory(addedVar)) {
+				if (fragment.isInCategory(addedVar)) {
 					if (editedInstance != null) {
-						activity.removeFromAdapter(editedInstance);
+						fragment.removeFromAdapter(editedInstance);
 					}
-					activity.addToAdapter(addedVar);
+					fragment.addToAdapter(addedVar);
 				}
 
 				mathRegistry.save();
 
-				if (activity.isInCategory(addedVar)) {
-					activity.sort();
+				if (fragment.isInCategory(addedVar)) {
+					fragment.sort();
 				}
 			}
 		}
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/MathEntityRemover.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/MathEntityRemover.java
index 4e4370cb..866ed0c0 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/MathEntityRemover.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/MathEntityRemover.java
@@ -34,25 +34,25 @@ class MathEntityRemover<T extends MathEntity> implements DialogInterface.OnClick
 	private final CalculatorMathRegistry<? super T> varsRegistry;
 
 	@NotNull
-	private final AbstractMathEntityListActivity<T> activity;
+	private final AbstractMathEntityListFragment<T> fragment;
 
 	public MathEntityRemover(@NotNull T mathEntity,
 							 @Nullable DialogInterface.OnClickListener callbackOnCancel,
 							 @NotNull CalculatorMathRegistry<? super T> varsRegistry,
-							 @NotNull AbstractMathEntityListActivity<T> activity) {
-		this(mathEntity, callbackOnCancel, false, varsRegistry, activity);
+							 @NotNull AbstractMathEntityListFragment<T> fragment) {
+		this(mathEntity, callbackOnCancel, false, varsRegistry, fragment);
 	}
 
 	public MathEntityRemover(@NotNull T mathEntity,
 							 @Nullable DialogInterface.OnClickListener callbackOnCancel,
 							 boolean confirmed,
 							 @NotNull CalculatorMathRegistry<? super T> varsRegistry,
-							 @NotNull AbstractMathEntityListActivity<T> activity) {
+							 @NotNull AbstractMathEntityListFragment<T> fragment) {
 		this.mathEntity = mathEntity;
 		this.callbackOnCancel = callbackOnCancel;
 		this.confirmed = confirmed;
 		this.varsRegistry = varsRegistry;
-		this.activity = activity;
+		this.fragment = fragment;
 	}
 
 	@Override
@@ -60,28 +60,28 @@ class MathEntityRemover<T extends MathEntity> implements DialogInterface.OnClick
 		if (!confirmed) {
 			showConfirmationDialog();
 		} else {
-			if (activity.isInCategory(mathEntity)) {
-				activity.removeFromAdapter(mathEntity);
+			if (fragment.isInCategory(mathEntity)) {
+				fragment.removeFromAdapter(mathEntity);
 			}
 
 			varsRegistry.remove(mathEntity);
 			varsRegistry.save();
-			if (activity.isInCategory(mathEntity)) {
-				activity.notifyAdapter();
+			if (fragment.isInCategory(mathEntity)) {
+				fragment.notifyAdapter();
 			}
 		}
 	}
 
 	public void showConfirmationDialog() {
-		final TextView question = new TextView(activity);
-		question.setText(String.format(activity.getString(R.string.c_var_removal_confirmation_question), mathEntity.getName()));
+		final TextView question = new TextView(fragment.getActivity());
+		question.setText(String.format(fragment.getString(R.string.c_var_removal_confirmation_question), mathEntity.getName()));
 		question.setPadding(6, 6, 6, 6);
-		final AlertDialog.Builder builder = new AlertDialog.Builder(activity)
+		final AlertDialog.Builder builder = new AlertDialog.Builder(fragment.getActivity())
 				.setCancelable(true)
 				.setView(question)
 				.setTitle(R.string.c_var_removal_confirmation)
 				.setNegativeButton(R.string.c_no, callbackOnCancel)
-				.setPositiveButton(R.string.c_yes, new MathEntityRemover<T>(mathEntity, callbackOnCancel, true, varsRegistry, activity));
+				.setPositiveButton(R.string.c_yes, new MathEntityRemover<T>(mathEntity, callbackOnCancel, true, varsRegistry, fragment));
 
 		builder.create().show();
 	}
diff --git a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/VarEditorSaver.java b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/VarEditorSaver.java
index 1c72d484..3cf186e5 100644
--- a/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/VarEditorSaver.java
+++ b/calculatorpp/src/main/java/org/solovyev/android/calculator/math/edit/VarEditorSaver.java
@@ -32,7 +32,7 @@ import org.solovyev.common.text.StringUtils;
 class VarEditorSaver<T extends MathEntity> implements DialogInterface.OnClickListener {
 
 	public static interface EditorCreator<T extends MathEntity> {
-		void showEditor(@NotNull AbstractMathEntityListActivity<T> activity,
+		void showEditor(@NotNull AbstractMathEntityListFragment<T> activity,
 						@Nullable T editedInstance,
 						@Nullable String name,
 						@Nullable String value,
@@ -52,7 +52,7 @@ class VarEditorSaver<T extends MathEntity> implements DialogInterface.OnClickLis
 	private final CalculatorMathRegistry<T> mathRegistry;
 
 	@NotNull
-	private final AbstractMathEntityListActivity<T> activity;
+	private final AbstractMathEntityListFragment<T> fragment;
 
 	@NotNull
 	private View editView;
@@ -60,13 +60,13 @@ class VarEditorSaver<T extends MathEntity> implements DialogInterface.OnClickLis
 	public VarEditorSaver(@NotNull MathEntityBuilder<? extends T> varBuilder,
 						  @Nullable T editedInstance,
 						  @NotNull View editView,
-						  @NotNull AbstractMathEntityListActivity<T> activity,
+						  @NotNull AbstractMathEntityListFragment<T> fragment,
 						  @NotNull CalculatorMathRegistry<T> mathRegistry,
 						  @NotNull EditorCreator<T> editorCreator) {
 		this.varBuilder = varBuilder;
 		this.editedInstance = editedInstance;
 		this.editView = editView;
-		this.activity = activity;
+		this.fragment = fragment;
 		this.mathRegistry = mathRegistry;
 		this.editorCreator = editorCreator;
 	}
@@ -109,7 +109,7 @@ class VarEditorSaver<T extends MathEntity> implements DialogInterface.OnClickLis
 							error = null;
 						} else {
 							// value is not empty => must be a number
-							boolean valid = CalculatorVarsActivity.isValidValue(value);
+							boolean valid = CalculatorVarsFragment.isValidValue(value);
 
 							if (valid) {
 								varBuilder.setName(name);
@@ -131,21 +131,21 @@ class VarEditorSaver<T extends MathEntity> implements DialogInterface.OnClickLis
 			}
 
 			if (error != null) {
-				Toast.makeText(activity, activity.getString(error), Toast.LENGTH_LONG).show();
-				editorCreator.showEditor(activity, editedInstance, name, value, description);
+				Toast.makeText(fragment.getActivity(), fragment.getString(error), Toast.LENGTH_LONG).show();
+				editorCreator.showEditor(fragment, editedInstance, name, value, description);
 			} else {
 				final T addedVar = mathRegistry.add(varBuilder);
-				if (activity.isInCategory(addedVar)) {
+				if (fragment.isInCategory(addedVar)) {
 					if (editedInstance != null) {
-						activity.removeFromAdapter(editedInstance);
+						fragment.removeFromAdapter(editedInstance);
 					}
-					activity.addToAdapter(addedVar);
+					fragment.addToAdapter(addedVar);
 				}
 
 				mathRegistry.save();
 
-				if (activity.isInCategory(addedVar)) {
-					activity.sort();
+				if (fragment.isInCategory(addedVar)) {
+					fragment.sort();
 				}
 			}
 		}