diff --git a/android-app/src/main/res/layout/function_edit_param.xml b/android-app/src/main/res/layout/function_edit_param.xml
index 4b4db28e..47ee0b36 100644
--- a/android-app/src/main/res/layout/function_edit_param.xml
+++ b/android-app/src/main/res/layout/function_edit_param.xml
@@ -23,30 +23,34 @@
   -->
 
 <LinearLayout xmlns:a="http://schemas.android.com/apk/res/android"
-	a:layout_width="match_parent"
-	a:layout_height="wrap_content"
-	a:orientation="horizontal">
+			  xmlns:tools="http://schemas.android.com/tools"
+			  a:layout_width="match_parent"
+			  a:layout_height="wrap_content"
+			  a:orientation="horizontal">
 
 	<Button
 		a:id="@+id/function_remove_param_button"
 		a:layout_width="0dp"
 		a:layout_height="wrap_content"
 		a:layout_weight="1"
-		a:text="-" />
+		a:text="−"
+		tools:ignore="HardcodedText"/>
 
 	<Button
 		a:id="@+id/function_up_param_button"
 		a:layout_width="0dp"
 		a:layout_height="wrap_content"
 		a:layout_weight="1"
-		a:text="↑" />
+		a:text="↑"
+		tools:ignore="HardcodedText"/>
 
 	<Button
 		a:id="@+id/function_down_param_button"
 		a:layout_width="0dp"
 		a:layout_height="wrap_content"
 		a:layout_weight="1"
-		a:text="↓" />
+		a:text="↓"
+		tools:ignore="HardcodedText"/>
 
 	<org.solovyev.android.calculator.function.FunctionParamEditText
 		a:id="@+id/function_param_edit_text"
@@ -54,6 +58,6 @@
 		a:layout_width="0dp"
 		a:layout_height="wrap_content"
 		a:layout_weight="3"
-		a:inputType="text" />
+		a:inputType="text"/>
 
 </LinearLayout>
diff --git a/core/src/main/java/org/solovyev/android/calculator/AbstractNumberBuilder.java b/core/src/main/java/org/solovyev/android/calculator/AbstractNumberBuilder.java
index 18777fb8..056ef889 100644
--- a/core/src/main/java/org/solovyev/android/calculator/AbstractNumberBuilder.java
+++ b/core/src/main/java/org/solovyev/android/calculator/AbstractNumberBuilder.java
@@ -79,7 +79,8 @@ public abstract class AbstractNumberBuilder {
 
 	private boolean isSignAfterE(@Nonnull MathType.Result mathTypeResult) {
 		if (!isHexMode()) {
-			if ("-".equals(mathTypeResult.getMatch()) || "+".equals(mathTypeResult.getMatch())) {
+			final String match = mathTypeResult.getMatch();
+			if ("−".equals(match) || "-".equals(match) || "+".equals(match)) {
 				final StringBuilder localNb = numberBuilder;
 				if (localNb != null && localNb.length() > 0) {
 					if (localNb.charAt(localNb.length() - 1) == MathType.POWER_10) {