diff --git a/pom.xml b/pom.xml
index 285d7d5d..41342c1f 100644
--- a/pom.xml
+++ b/pom.xml
@@ -13,7 +13,7 @@
 		<maven.compiler.target>1.8</maven.compiler.target>
 		<maven.compiler.source>1.8</maven.compiler.source>
 		<slf4j.version>1.7.15</slf4j.version>
-		<junit.version>4.11</junit.version>
+		<junit.version>4.13.2</junit.version>
 	</properties>
 
 	<repositories>
@@ -73,7 +73,7 @@
 		<dependency>
 			<groupId>com.google.guava</groupId>
 			<artifactId>guava</artifactId>
-			<version>23.6-jre</version>
+			<version>31.0.1-jre</version>
 		</dependency>
 
 		<!-- JMH Benchmark -->
@@ -111,22 +111,6 @@
 			<version>${junit.version}</version>
 			<scope>test</scope>
 		</dependency>
-
-		<!-- JMH Benchmark -->
-		<dependency>
-			<groupId>org.openjdk.jmh</groupId>
-			<artifactId>jmh-core</artifactId>
-			<version>1.19</version>
-			<scope>test</scope>
-		</dependency>
-		<dependency>
-			<groupId>org.openjdk.jmh</groupId>
-			<artifactId>jmh-generator-annprocess</artifactId>
-			<version>1.19</version>
-			<scope>test</scope>
-		</dependency>
-		<!-- End JMH Benchmark -->
-
 		<!-- ~~~~~~~~~~~~~~~~~~~ End Testing ~~~~~~~~~~~~~~~~~~~~~~ -->
 	</dependencies>
 
diff --git a/src/main/java/org/aksw/simba/lemming/ColouredGraph.java b/src/main/java/org/aksw/simba/lemming/ColouredGraph.java
index 2133e33f..f9430702 100644
--- a/src/main/java/org/aksw/simba/lemming/ColouredGraph.java
+++ b/src/main/java/org/aksw/simba/lemming/ColouredGraph.java
@@ -1,14 +1,6 @@
 package org.aksw.simba.lemming;
 
-import grph.DefaultIntSet;
-import grph.Grph;
-import grph.GrphAlgorithmCache;
-import grph.algo.MultiThreadProcessing;
-import grph.in_memory.InMemoryGrph;
-import it.unimi.dsi.fastutil.ints.IntSet;
-
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -25,6 +17,13 @@
 import com.carrotsearch.hppc.BitSet;
 import com.carrotsearch.hppc.ObjectArrayList;
 
+import grph.DefaultIntSet;
+import grph.Grph;
+import grph.GrphAlgorithmCache;
+import grph.algo.MultiThreadProcessing;
+import grph.in_memory.InMemoryGrph;
+import it.unimi.dsi.fastutil.ints.IntSet;
+
 public class ColouredGraph {
 
 	private static final Logger LOGGER = LoggerFactory.getLogger(ColouredGraph.class);
@@ -36,13 +35,13 @@ public class ColouredGraph {
     protected ColourPalette edgePalette;
     protected ColourPalette dtEdgePalette;
 
-    /*
+    /**
      * 1st key: vertex ID, 2nd key: data typed property and the values is the value
      * of the literal
      */
     protected Map<Integer, Map<BitSet, List<String>>> mapVertexIdAndLiterals;
 
-    /*
+    /**
      * map for storing type of literal accordingly to the data typed property edge
      */
     protected Map<BitSet, String> mapLiteralTypes;
@@ -324,25 +323,11 @@ public ColouredGraph copy() {
     }
 
     public int getTailOfTheEdge(int edgeId) {
-        IntSet vertices = graph.getVerticesIncidentToEdge(edgeId);
-        if (vertices.size() > 0) {
-            int[] arrVertIDs = vertices.toIntArray();
-            return arrVertIDs[0];
-        }
-        return -1;
+        return graph.getDirectedSimpleEdgeTail(edgeId);
     }
 
     public int getHeadOfTheEdge(int edgeId) {
-        IntSet vertices = graph.getVerticesIncidentToEdge(edgeId);
-        if (vertices.size() > 0) {
-            int[] arrVertIDs = vertices.toIntArray();
-            if (arrVertIDs.length == 1) {
-                return arrVertIDs[0];
-            } else {
-                return arrVertIDs[1];
-            }
-        }
-        return -1;
+        return graph.getDirectedSimpleEdgeHead(edgeId);
     }
 
     /**
diff --git a/src/test/java/org/aksw/simba/lemming/creation/EdgeHeadTailSelectionTest.java b/src/test/java/org/aksw/simba/lemming/creation/EdgeHeadTailSelectionTest.java
new file mode 100644
index 00000000..4456eb24
--- /dev/null
+++ b/src/test/java/org/aksw/simba/lemming/creation/EdgeHeadTailSelectionTest.java
@@ -0,0 +1,54 @@
+package org.aksw.simba.lemming.creation;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import org.aksw.simba.lemming.ColouredGraph;
+import org.apache.jena.rdf.model.Model;
+import org.apache.jena.rdf.model.ModelFactory;
+import org.junit.Assert;
+import org.junit.Test;
+
+import it.unimi.dsi.fastutil.ints.IntSet;
+
+/**
+ * This test checks whether the requested head and tail IDs for edges make
+ * sense. Related to issue #31 (https://github.com/dice-group/Lemming/issues/31).
+ * 
+ * @author Michael R&ouml;der (michael.roeder@uni-paderborn.de)
+ *
+ */
+public class EdgeHeadTailSelectionTest {
+
+    private static final String GRAPH_FILE1 = "head_tail_edge_selection.n3";
+
+    @Test
+    public void testcase1() throws IOException {
+        Model model = ModelFactory.createDefaultModel();
+        try (InputStream is = this.getClass().getClassLoader().getResourceAsStream(GRAPH_FILE1);) {
+            model.read(is, null, "N3");
+        }
+
+        GraphCreator creator = new GraphCreator();
+        ColouredGraph graph = creator.processModel(model);
+
+        int numberOfVertices = graph.getVertices().size();
+        IntSet edges;
+        for (int v = 0; v < numberOfVertices; ++v) {
+            edges = graph.getOutEdges(v);
+            for (int edge : edges) {
+                Assert.assertEquals(
+                        "Found an outgoing edge of " + v
+                                + " that has a tail with a different ID. That shouldn't happen!",
+                        v, graph.getTailOfTheEdge(edge));
+            }
+            edges = graph.getInEdges(v);
+            for (int edge : edges) {
+                Assert.assertEquals(
+                        "Found an incoming edge of " + v
+                                + " that has a head with a different ID. That shouldn't happen!",
+                        v, graph.getHeadOfTheEdge(edge));
+            }
+        }
+    }
+}
diff --git a/src/test/resources/head_tail_edge_selection.n3 b/src/test/resources/head_tail_edge_selection.n3
new file mode 100644
index 00000000..be622cac
--- /dev/null
+++ b/src/test/resources/head_tail_edge_selection.n3
@@ -0,0 +1,8 @@
+<http://example.org/entity1> <http://example.org/relation1> <http://example.org/entity2> .
+<http://example.org/entity1> <http://example.org/relation1> <http://example.org/entity3> .
+<http://example.org/entity14> <http://example.org/relation1> <http://example.org/entity2> .
+<http://example.org/entity10> <http://example.org/relation1> <http://example.org/entity2> .
+<http://example.org/entity10> <http://example.org/relation1> <http://example.org/entity3> .
+<http://example.org/entity10> <http://example.org/relation2> <http://example.org/entity3> .
+<http://example.org/entity10> <http://example.org/relation3> <http://example.org/entity2> .
+<http://example.org/entity1> <http://example.org/relation4> <http://example.org/entity10> .