diff --git a/README.md b/README.md
index 5287fedeb..b6111e433 100644
--- a/README.md
+++ b/README.md
@@ -11,10 +11,10 @@ Digital is a easy-to-use digital logic designer and circuit simulator designed f
 
 ## Installation ##
 
-There is no installation necessary, just unpack the *Digital.zip* file, which is
+There is no installation required, just unpack the *Digital.zip* file, which is
 available for [download](https://github.com/hneemann/Digital/releases/latest).
-On Windows machines the EXE file can be executed, on Linux and MacOS the
-JAR file can be started directly.
+On Windows machines the EXE file can be executed, on Linux start the shell script
+and on MacOS the JAR file can be started directly.
 A [Java Runtime Environment](https://www.java.com/) (at least JRE 8) is required
 to run Digital.
 
@@ -235,9 +235,9 @@ If you want to build Digital from the source code:
 ## Credits ##
 
 * The verilog code generator and almost all the necessary verilog templates where implemented
-  by Ivan de Jesus Deras Tabora, a faculty member at Universidad Tecnológica Centroamericana in Honduras.
-* The Portuguese translation was provided by Theldo Cruz Franqueira, a faculty member at
-  Pontifícia Universidade Católica de Minas Gerais in Brazil.
+  by Ivan de Jesus Deras Tabora; Universidad Tecnológica Centroamericana; Honduras.
+* The Portuguese translation was provided by Theldo Cruz Franqueira;
+  Pontifícia Universidade Católica de Minas Gerais; Brazil.
 
 ## Additional Screenshots
 
diff --git a/src/main/resources/lang/lang.xml b/src/main/resources/lang/lang.xml
index a4054865b..f0a41244b 100644
--- a/src/main/resources/lang/lang.xml
+++ b/src/main/resources/lang/lang.xml
@@ -11,7 +11,7 @@ The file "lang_xx_ref.xml" is important because it helps me
 to keep track of future changes to the language files.
 
 If you also want to translate the static part of the documentation,
-you have to translate one of the files "static_xx.xml" from the
+you have to translate the file "static_en.xml" from the
 folder "src/test/Resources/Docu".
 
 You can test the translation by simply putting the files into
@@ -20,6 +20,15 @@ the Digital.jar file. It's not necessary to rebuild the jar.
 If you are satisfied with the translation, please send me the
 translated version AND the file "lang_xx_ref.xml" you used for the
 translation!
+
+If keys are added to or changed in the future, the keys must first
+be copied unchanged to the reference file. They can then be added
+or updated in the corresponding language file. The idea is to
+always keep the reference file synchronous with the language file.
+In this way it can be recognized whether a translation needs to
+be revised or not: This is always the case if a text from the
+English language file no longer matches the text in the reference
+file.
 -->
 <languages>
     <lang name="en">English</lang>
diff --git a/src/test/java/de/neemann/digital/lang/TestLang.java b/src/test/java/de/neemann/digital/lang/TestLang.java
index 775bc4f38..b02769252 100644
--- a/src/test/java/de/neemann/digital/lang/TestLang.java
+++ b/src/test/java/de/neemann/digital/lang/TestLang.java
@@ -105,7 +105,7 @@ public class TestLang extends TestCase {
                 obsolete.add(k);
 
             String val = langResources.get(k);
-            assertFalse(l+"; "+k+"; not trimmed: >" + val + "<", !val.contains("\n") && !val.equals(val.trim()));
+            assertFalse(l + "; " + k + "; not trimmed: >" + val + "<", !val.contains("\n") && !val.equals(val.trim()));
         }
         if (!obsolete.isEmpty()) {
             System.out.println("Obsolete language keys for: " + l);
@@ -116,12 +116,12 @@ public class TestLang extends TestCase {
         }
 
         ArrayList<String> modified = new ArrayList<>();
-        de.neemann.gui.language.Resources origResource =
+        de.neemann.gui.language.Resources refResource =
                 new de.neemann.gui.language.Resources(
                         getClass().getClassLoader().getResourceAsStream("lang/lang_" + l.getName() + "_ref.xml"));
         for (String k : master.getKeys()) {
             String m = master.get(k);
-            String o = origResource.get(k);
+            String o = refResource.get(k);
             if (m != null && o != null && !m.equals(o))
                 modified.add(k);
         }
@@ -131,11 +131,23 @@ public class TestLang extends TestCase {
             missing.sort(String::compareTo);
             for (String k : modified) {
                 System.out.println("  key: " + k);
-                System.out.println("    old: " + origResource.get(k));
+                System.out.println("    old: " + refResource.get(k));
                 System.out.println("    new: " + master.get(k));
                 System.out.println("    old: " + langResources.get(k));
             }
         }
+
+        ArrayList<String> missingInRef = new ArrayList<>();
+        for (String k : langKeys)
+            if (refResource.get(k) == null)
+                missingInRef.add(k);
+
+        if (!missingInRef.isEmpty()) {
+            System.out.println("Missing keys in the reference file for: " + l);
+            for (String k : missingInRef) {
+                System.out.println("    " + k);
+            }
+        }
     }
 
     public static File getSourceFiles() {