diff --git a/src/main/java/de/ids_mannheim/korap/query/SpanExpansionQuery.java b/src/main/java/de/ids_mannheim/korap/query/SpanExpansionQuery.java
index 33c5b5e..cab5683 100644
--- a/src/main/java/de/ids_mannheim/korap/query/SpanExpansionQuery.java
+++ b/src/main/java/de/ids_mannheim/korap/query/SpanExpansionQuery.java
@@ -19,7 +19,8 @@
  * */
 public class SpanExpansionQuery extends SimpleSpanQuery{
 
-	int min, max;
+	int min, max; 
+	byte classNumber;
 	boolean isBefore;
 	
 	public SpanExpansionQuery(SpanQuery firstClause, int min, int max,  
@@ -29,6 +30,12 @@
 		this.max = max;
 		this.isBefore = isBefore;
 	}
+	
+	public SpanExpansionQuery(SpanQuery firstClause, int min, int max, 
+			byte classNumber, boolean isBefore, boolean collectPayloads) {		
+		this(firstClause, min,max,isBefore,collectPayloads);
+		this.classNumber = classNumber;
+	}
 
 	@Override
 	public SimpleSpanQuery clone() {
@@ -87,4 +94,12 @@
 	public void setBefore(boolean isBefore) {
 		this.isBefore = isBefore;
 	}
+
+	public byte getClassNumber() {
+		return classNumber;
+	}
+
+	public void setClassNumber(byte classNumber) {
+		this.classNumber = classNumber;
+	}
 }
diff --git a/src/main/java/de/ids_mannheim/korap/query/SpanNextQuery.java b/src/main/java/de/ids_mannheim/korap/query/SpanNextQuery.java
index a15d80d..7274826 100644
--- a/src/main/java/de/ids_mannheim/korap/query/SpanNextQuery.java
+++ b/src/main/java/de/ids_mannheim/korap/query/SpanNextQuery.java
@@ -24,8 +24,6 @@
  */
 public class SpanNextQuery extends SimpleSpanQuery implements Cloneable {
 
-    private String spanName;
-
 	// Constructor
     public SpanNextQuery(SpanQuery firstClause, SpanQuery secondClause) {
     	this(firstClause, secondClause, true);
@@ -35,10 +33,14 @@
     public SpanNextQuery(SpanQuery firstClause, SpanQuery secondClause,
 		boolean collectPayloads) {   
     	super(firstClause, secondClause, collectPayloads);
-    	this.spanName = "spanNext";
     };
 
-
+    public SpanNextQuery(SpanQuery firstClause, SpanQuery secondClause, 
+    		boolean isFirstNegated, boolean collectPayloads) {   
+    	super(firstClause, secondClause, collectPayloads);
+    }
+    
+    
     @Override
     public Spans getSpans (final AtomicReaderContext context, Bits acceptDocs,
 		   Map<Term,TermContext> termContexts) throws IOException {	
@@ -59,8 +61,7 @@
     @Override
 	public String toString(String field) {
 		StringBuilder sb = new StringBuilder();
-		sb.append(this.spanName);
-		sb.append("(");
+		sb.append("spanNext(");
 		sb.append(firstClause.toString(field));
 	        sb.append(", ");
 		sb.append(secondClause.toString(field));
diff --git a/src/main/java/de/ids_mannheim/korap/query/SubspanQuery.java b/src/main/java/de/ids_mannheim/korap/query/SubspanQuery.java
index b01a37d..4af5e69 100644
--- a/src/main/java/de/ids_mannheim/korap/query/SubspanQuery.java
+++ b/src/main/java/de/ids_mannheim/korap/query/SubspanQuery.java
@@ -51,6 +51,8 @@
 	public String toString(String field) {		
 		StringBuilder sb = new StringBuilder();
 		sb.append("subspan(");
+		sb.append(this.firstClause.toString());
+		sb.append(",");
 		sb.append(this.startOffset);
 		sb.append(",");
 		sb.append(this.length);
diff --git a/src/main/java/de/ids_mannheim/korap/query/spans/ExpandedSpans.java b/src/main/java/de/ids_mannheim/korap/query/spans/ExpandedSpans.java
index 29c2d14..2f8ebed 100644
--- a/src/main/java/de/ids_mannheim/korap/query/spans/ExpandedSpans.java
+++ b/src/main/java/de/ids_mannheim/korap/query/spans/ExpandedSpans.java
@@ -1,6 +1,7 @@
 package de.ids_mannheim.korap.query.spans;
 
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -12,9 +13,13 @@
 
 import de.ids_mannheim.korap.query.SpanExpansionQuery;
 
+/**
+ * @author margaretha
+ * */
 public class ExpandedSpans extends SimpleSpans{
 	
 	private int min, max;
+	private byte classNumber;
 	private boolean isBefore;	
 	private List<CandidateSpan> candidateSpans;
 	private long matchCost;
@@ -25,6 +30,7 @@
 		super(spanExpansionQuery, context, acceptDocs, termContexts);
 		this.min = spanExpansionQuery.getMin();
 		this.max = spanExpansionQuery.getMax();
+		this.classNumber = spanExpansionQuery.getClassNumber();
 		this.isBefore = spanExpansionQuery.isBefore();
 		
 		candidateSpans = new ArrayList<CandidateSpan>();		
@@ -42,7 +48,7 @@
 		while (hasMoreSpans || candidateSpans.size() > 0) {
 			if (candidateSpans.size() > 0 ){
 				setMatch(candidateSpans.get(0));
-				candidateSpans.remove(0);
+				candidateSpans.remove(0);								
 				return true;
 			}
 			else {
@@ -55,17 +61,20 @@
 	
 	private void setCandidateList() throws IOException {
 		CandidateSpan cs;
-		int counter;
+		int counter, start, end;
+		
 		if (isBefore){
 			counter = max;
 			while (counter >= min ){
+				start =  Math.max(0,firstSpans.start() - counter);			
 				cs = new CandidateSpan(
-						firstSpans.start() - counter, 
+						start, 
 						firstSpans.end(), 
 						firstSpans.doc(), 
 						firstSpans.cost(), 
-						firstSpans.getPayload()
+						calculatePayload(start, firstSpans.start())
 				);
+								
 				candidateSpans.add(cs);
 				counter--;
 			}
@@ -73,18 +82,44 @@
 		else{
 			counter = min;
 			while (counter <= max){
+				// TODO: How do I know if the end is already too far (over the end of the doc)? 
+				end = firstSpans.end() + counter;
 				cs = new CandidateSpan(
 						firstSpans.start(), 
-						firstSpans.end() + counter, 
+						end, 
 						firstSpans.doc(), 
 						firstSpans.cost(), 
-						firstSpans.getPayload()
+						calculatePayload(firstSpans.end(), end)
 				);
 				candidateSpans.add(cs);
 				counter++;
 			}
 		}	
 	}
+	
+	private ArrayList<byte[]> calculatePayload(int start, int end)
+			throws IOException{
+		
+		ArrayList<byte[]> payload = new ArrayList<byte[]>();
+		
+		if (classNumber > 0 ){					
+			if (firstSpans.isPayloadAvailable()){				
+				payload.addAll(firstSpans.getPayload());
+			}
+			
+			//System.out.println("Extension offsets "+start+","+end);
+			payload.add(calculateExtensionOffsets(start, end));
+		}
+		return payload;
+	}
+	
+	private byte[] calculateExtensionOffsets(int start, int end) {
+		ByteBuffer buffer = ByteBuffer.allocate(9);
+		buffer.put(classNumber);
+		buffer.putInt(start);					
+		buffer.putInt(end);					
+		return buffer.array();
+	}
 
 	private void setMatch(CandidateSpan candidateSpan) {
 		matchDocNumber = candidateSpan.getDoc();
diff --git a/src/main/java/de/ids_mannheim/korap/query/spans/NextSpans.java b/src/main/java/de/ids_mannheim/korap/query/spans/NextSpans.java
index 9651cba..4936eaa 100644
--- a/src/main/java/de/ids_mannheim/korap/query/spans/NextSpans.java
+++ b/src/main/java/de/ids_mannheim/korap/query/spans/NextSpans.java
@@ -20,7 +20,7 @@
  *  
  *  Update: allow multiple matches at the same firstspan position
  *  
- * 	@author margaretha 
+ * 	@author margaretha, diewald
  * */
 public class NextSpans extends SimpleSpans {	
 	
diff --git a/src/test/java/de/ids_mannheim/korap/index/TestSpanExpansionIndex.java b/src/test/java/de/ids_mannheim/korap/index/TestSpanExpansionIndex.java
index d81878b..4c1704e 100644
--- a/src/test/java/de/ids_mannheim/korap/index/TestSpanExpansionIndex.java
+++ b/src/test/java/de/ids_mannheim/korap/index/TestSpanExpansionIndex.java
@@ -11,6 +11,7 @@
 import de.ids_mannheim.korap.KorapIndex;
 import de.ids_mannheim.korap.KorapMatch;
 import de.ids_mannheim.korap.KorapResult;
+import de.ids_mannheim.korap.query.SpanElementQuery;
 import de.ids_mannheim.korap.query.SpanExpansionQuery;
 
 public class TestSpanExpansionIndex {
@@ -18,14 +19,19 @@
 	KorapResult kr;
     KorapIndex ki;
     
-	@Test
-	public void testCase1() throws IOException {
-		ki = new KorapIndex();
+    public TestSpanExpansionIndex() throws IOException {
+    	ki = new KorapIndex();
 		for (String i : new String[] {"AAA-12402"}) {
 		    ki.addDocFile(
 		        getClass().getResource("/wiki/" + i + ".json.gz").getFile(),true);
 		};
 		ki.commit();
+	}
+    
+    /** Left and right expansions
+     * */
+	@Test
+	public void testCase1() throws IOException {
 		
 		SpanTermQuery stq = new SpanTermQuery(new Term("tokens","s:Kaiser")	);
 		SpanExpansionQuery seq = new SpanExpansionQuery(stq, 0, 2, true, true);		
@@ -57,4 +63,28 @@
 //		}	
 		
 	}
+	
+	/** Classnumber
+	 * 	Cannot check the correctness directly
+	 * */
+	@Test
+	public void testCase2() {
+		byte classNumber = 1;
+		
+		// create new payload for the expansion offsets
+		SpanTermQuery stq = new SpanTermQuery(new Term("tokens","s:Kaiser")	);
+		SpanExpansionQuery sq = new SpanExpansionQuery(stq, 0, 2, classNumber, true, true);		
+		kr = ki.search(sq, (short) 10);
+				
+		// add expansion offsets to the existing payload
+		SpanElementQuery seq = new SpanElementQuery("tokens", "cnx/c:np");
+		sq = new SpanExpansionQuery(seq, 1, 2, classNumber, false, true);		
+		kr = ki.search(sq, (short) 10);
+		
+		/*for (KorapMatch km : kr.getMatches()){		
+			System.out.println(km.getStartPos() +","+km.getEndPos()+" "
+				+km.getSnippetBrackets());
+		}*/
+	}
+	
 }