diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 0c9d86e..6fe0ecd 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -16,6 +16,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
       - name: Set up JDK 11
         uses: actions/setup-java@v3
         with:
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 5f66da6..b7c6b90 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -8,6 +8,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
       - name: Set up Java for publishing to Maven Central Repository
         uses: actions/setup-java@v3
         with:
diff --git a/README.md b/README.md
index 5ca530a..575fc79 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,7 @@ EvalEx - Java Expression Evaluator
 [![Security Rating](https://sonarcloud.io/api/project_badges/measure?project=ezylang_EvalEx&metric=security_rating)](https://sonarcloud.io/summary/new_code?id=ezylang_EvalEx)
 [![Vulnerabilities](https://sonarcloud.io/api/project_badges/measure?project=ezylang_EvalEx&metric=vulnerabilities)](https://sonarcloud.io/summary/new_code?id=ezylang_EvalEx)
 [![Coverage](https://sonarcloud.io/api/project_badges/measure?project=ezylang_EvalEx&metric=coverage)](https://sonarcloud.io/summary/new_code?id=ezylang_EvalEx)
+[![Maven Central](https://img.shields.io/maven-central/v/com.ezylang/EvalEx.svg?label=Maven%20Central)](https://search.maven.org/search?q=a:%22EvalEx%22)
 
 | :warning: Version 3 of EvalEx is a complete rewrite of the popular expression evaluator. See [the new documentation area](https://ezylang.github.io/EvalEx/concepts/changes.html) for an overview of the changes.   |
 |---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
@@ -41,6 +42,13 @@ on [GitHub Pages](https://ezylang.github.io/EvalEx/)
 For announcements, questions and ideas visit
 the [Discussions area](https://github.com/ezylang/EvalEx/discussions).
 
+## Download / Including
+
+You can download the binaries, source code and JavaDoc jars from
+[Maven Central](https://search.maven.org/search?q=a:%22EvalEx%22).\
+You will find there also copy/paste templates for including EvalEx in your project with build
+systems like Maven or Gradle.
+
 ## Examples
 
 ### A simple example, that shows how it works in general:
diff --git a/src/main/java/com/ezylang/evalex/Expression.java b/src/main/java/com/ezylang/evalex/Expression.java
index 5b53736..5f88735 100644
--- a/src/main/java/com/ezylang/evalex/Expression.java
+++ b/src/main/java/com/ezylang/evalex/Expression.java
@@ -332,10 +332,10 @@ public class Expression {
   }
 
   /**
-   * Returns all variables or constants that are used i the expression, excluding the standard
-   * constants like e.g. <code>PI</code> or <code>TRUE</code> and <code>FALSE</code>.
+   * Returns all variables that are used i the expression, excluding the constants like e.g. <code>
+   * PI</code> or <code>TRUE</code> and <code>FALSE</code>.
    *
-   * @return All used variables and constants less the standard constants.
+   * @return All used variables excluding constants.
    * @throws ParseException If there were problems while parsing the expression.
    */
   public Set<String> getUsedVariables() throws ParseException {
@@ -350,4 +350,20 @@ public class Expression {
 
     return variables;
   }
+
+  /**
+   * Returns all variables that are used in the expression, but have no value assigned.
+   *
+   * @return All variables that have no value assigned.
+   * @throws ParseException If there were problems while parsing the expression.
+   */
+  public Set<String> getUndefinedVariables() throws ParseException {
+    Set<String> variables = new TreeSet<>(String.CASE_INSENSITIVE_ORDER);
+    for (String variable : getUsedVariables()) {
+      if (getDataAccessor().getData(variable) == null) {
+        variables.add(variable);
+      }
+    }
+    return variables;
+  }
 }
diff --git a/src/test/java/com/ezylang/evalex/ExpressionTest.java b/src/test/java/com/ezylang/evalex/ExpressionTest.java
index e0ffad5..ba9cf0b 100644
--- a/src/test/java/com/ezylang/evalex/ExpressionTest.java
+++ b/src/test/java/com/ezylang/evalex/ExpressionTest.java
@@ -145,4 +145,10 @@ class ExpressionTest {
     Expression expression = new Expression("a+B*b-A/PI*(1/2)*pi+e-E+a");
     assertThat(expression.getUsedVariables()).containsExactlyInAnyOrder("a", "b");
   }
+
+  @Test
+  void testGetUndefinedVariables() throws ParseException {
+    Expression expression = new Expression("a+A+b+B+c+C+E+e+PI+x").with("x", 1);
+    assertThat(expression.getUndefinedVariables()).containsExactlyInAnyOrder("a", "b", "c");
+  }
 }