diff --git a/dmnverifierapi/src/main/java/de/unikoblenz/fgbks/base/utils/boundary/bicreater/BiCreaterStringLowerBounds.java b/dmnverifierapi/src/main/java/de/unikoblenz/fgbks/base/utils/boundary/bicreater/BiCreaterStringLowerBounds.java
index 741c406a9ace324fa0885d0c75151e5b1a6be86e..e789e31a0529a62b671db46e0858bed3e82e9a07 100644
--- a/dmnverifierapi/src/main/java/de/unikoblenz/fgbks/base/utils/boundary/bicreater/BiCreaterStringLowerBounds.java
+++ b/dmnverifierapi/src/main/java/de/unikoblenz/fgbks/base/utils/boundary/bicreater/BiCreaterStringLowerBounds.java
@@ -22,6 +22,8 @@ public class BiCreaterStringLowerBounds extends AbstractBoundaryBiCreater<String
 
   @Override
   public Optional<StringBoundary> create(StringBoundary b1, StringBoundary b2) {
+    // Not supported for String Boundary
+    // Check BiCreaterStringBetween.
     return Optional.empty();
   }
 }
diff --git a/dmnverifierapi/src/main/java/de/unikoblenz/fgbks/base/utils/boundary/bicreater/BiCreaterStringUpperBounds.java b/dmnverifierapi/src/main/java/de/unikoblenz/fgbks/base/utils/boundary/bicreater/BiCreaterStringUpperBounds.java
index 27f0124244ed1cdf62a7ad0c15c0462f68da3ad8..1f449d7026741e5904c719a24d9c8b6d071cbf0b 100644
--- a/dmnverifierapi/src/main/java/de/unikoblenz/fgbks/base/utils/boundary/bicreater/BiCreaterStringUpperBounds.java
+++ b/dmnverifierapi/src/main/java/de/unikoblenz/fgbks/base/utils/boundary/bicreater/BiCreaterStringUpperBounds.java
@@ -22,6 +22,8 @@ public class BiCreaterStringUpperBounds extends AbstractBoundaryBiCreater<String
 
   @Override
   public Optional<StringBoundary> create(StringBoundary b1, StringBoundary b2) {
+    // Not supported for String Boundary
+    // Check BiCreaterStringBetween.
     return Optional.empty();
   }
 }