diff --git a/Changes b/Changes
index c770400..d1ccfc2 100644
--- a/Changes
+++ b/Changes
@@ -1,3 +1,6 @@
+0.43 2024-06-11
+    - [feature] Support opProx in C2 (bodmer)
+
 0.42 2024-01-11
     - [feature] Support #REG in C2 (bodmer)
     - [bugfix] Fix comma in #BED in C2 (bodmer)
diff --git a/pom.xml b/pom.xml
index b409fe5..049b395 100644
--- a/pom.xml
+++ b/pom.xml
@@ -4,7 +4,7 @@
 
 	<groupId>de.ids-mannheim.korap.koral</groupId>
 	<artifactId>Koral</artifactId>
-	<version>0.42.0</version>
+	<version>0.43.0</version>
 	<packaging>jar</packaging>
 	<name>Koral</name>
 	<url>https://korap.ids-mannheim.de</url>
diff --git a/src/main/antlr/cosmas/c2ps_opPROX.g b/src/main/antlr/cosmas/c2ps_opPROX.g
index 1569d1a..58e00f4 100644
--- a/src/main/antlr/cosmas/c2ps_opPROX.g
+++ b/src/main/antlr/cosmas/c2ps_opPROX.g
@@ -38,8 +38,8 @@
 // e.g. /w5umin -> remain = 'umin'.
 
 PROX_REMAIN
-	: (',')? ('b'..'h'|'j'..'l'|'n'|'o'|'q'|'r'|'u'|'v'|'y'|'z'|'B'..'H'|'J'..'L'|'N'|'O'|'Q'|'R'|'U'|'V'|'Y'|'Z') (~ ' ')* ;
-
+	: ~(','|'a'|'i'|'m'|'n'|'p'|'s'|'t'|'w'|'x'|'A'|'I'|'M'|'N'|'P'|'S'|'T'|'W'|'X'|'0'..'9'|'+'|'-'|':'|'/'|'%')  (~ ' ')*  ;
+	
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 //
 // 						PROX-Parser
@@ -102,4 +102,4 @@
 	|	('max'|'MAX') -> ^(GRP MAX);
 	
 
-	
\ No newline at end of file
+	
diff --git a/src/main/java/de/ids_mannheim/korap/query/parse/cosmas/c2ps_opPROX.java b/src/main/java/de/ids_mannheim/korap/query/parse/cosmas/c2ps_opPROX.java
index 6229719..737c7ad 100644
--- a/src/main/java/de/ids_mannheim/korap/query/parse/cosmas/c2ps_opPROX.java
+++ b/src/main/java/de/ids_mannheim/korap/query/parse/cosmas/c2ps_opPROX.java
@@ -15,12 +15,121 @@
 public class c2ps_opPROX 
 
 {
-	final static boolean bDebug = false;
+	final static boolean 
+		bDebug = false;
+	
+	public static final int MLANG_ENGLISH = 0;
+	public static final int MLANG_GERMAN  = 1;
+	
+	public static int
+		messLang = MLANG_ENGLISH; // default.
 	
 	// type of an Error CommonToken:
-	final static int typeERROR = 1; 
+	final static int 
+		typeERROR = 1; 
+	
 	// Prox error codes defined in StatusCodes.java.
 	
+	private static String getErrMessEN(int errCode, String text)
+	
+	{
+	switch( errCode )
+		{
+	case StatusCodes.ERR_PROX_MEAS_NULL:
+		return String.format("Proximity operator at '%s': one of the following prox. types is missing: w,s,p!", text);
+
+	case StatusCodes.ERR_PROX_MEAS_TOOGREAT:
+		return String.format("Proximity operator at '%s': Please, specify only 1 of the following prox. types: w,s,p! " +
+							 "It is possible to specify several at once by separating them with a ','. E.g.: ' /+w2,s2,p0 '.", text);
+		
+	case StatusCodes.ERR_PROX_VAL_NULL:
+		return String.format("Proximity operator at '%s': please specify a numerical value for the distance. E.g. ' /+w5 '.", text);
+		
+	case StatusCodes.ERR_PROX_VAL_TOOGREAT:
+		return String.format("Proximity operator at '%s': please specify only 1 distance value. E.g. ' /+w5 '.", text);
+		
+	case StatusCodes.ERR_PROX_DIR_TOOGREAT:
+		return String.format("Proximity operator at '%s': please specify either '+' or '-' or none of them for the direction.", text);
+		
+	case StatusCodes.ERR_PROX_WRONG_CHARS:
+		return String.format("Proximity operator at '%s': unknown proximity options!", text);
+		
+	case StatusCodes.UNKNOWN_QUERY_ERROR:
+		return String.format("Unknown error!");
+		
+	default:
+		return String.format("Proximity operator at '%s': unknown error. The correct syntax looks like this: E.g. ' /+w2 ' or ' /w10,s0 '.", text);
+		}	
+	}
+	
+	private static String getErrMessGE(int errCode, String text)
+
+	{
+	switch( errCode )
+		{
+	case StatusCodes.ERR_PROX_MEAS_NULL:
+		return String.format("Abstandsoperator an der Stelle '%s': es fehlt eine der folgenden Angaben: w,s,p!", text);
+		
+	case StatusCodes.ERR_PROX_MEAS_TOOGREAT:
+		return String.format("Abstandsoperator an der Stelle '%s': Bitte nur 1 der folgenden Angaben einsetzen: w,s,p! " +
+							 "Falls Mehrfachangabe erwünscht, müssen diese durch Kommata getrennt werden (z.B.: ' /+w2,s2,p0 ').", text);
+		
+	case StatusCodes.ERR_PROX_VAL_NULL:
+		return String.format("Abstandsoperator an der Stelle '%s': Bitte einen numerischen Wert einsetzen (z.B. ' /+w5 ')! ", text);
+		
+	case StatusCodes.ERR_PROX_VAL_TOOGREAT:
+		return String.format("Abstandsoperator an der Stelle '%s': Bitte nur 1 numerischen Wert einsetzen (z.B. ' /+w5 ')! ", text);
+		
+	case StatusCodes.ERR_PROX_DIR_TOOGREAT:
+		return String.format("Abstandsoperator an der Stelle '%s': Bitte nur 1 Angabe '+' oder '-' oder keine! ", text);
+		
+	case StatusCodes.ERR_PROX_WRONG_CHARS:
+		return String.format("Abstandsoperator an der Stelle '%s': unbekannte Abstandsoption(en)!", text);
+		
+	case StatusCodes.UNKNOWN_QUERY_ERROR:
+		return String.format("Unbekannter Fehler!");
+		
+	default:
+		return String.format("Abstandsoperator an der Stelle '%s': unbekannter Fehler. Korrekte Syntax z.B.: ' /+w2 ' oder ' /w10,s0 '.", text);
+		}
+	}
+	
+	private static String getErrMess(int errCode, int messLang, String text)
+	
+	{
+	if( messLang == c2ps_opPROX.MLANG_GERMAN )
+		return getErrMessGE(errCode, text);
+	else
+		return getErrMessEN(errCode, text);	
+	}
+
+
+	/**
+	 * in this version, the pre-stored message language is used.
+	 * @param errCode
+	 * @param text
+	 * @return
+	 * 10.06.24/FB
+	 */
+	
+	public static String getErrMess(int errCode, String text)
+	
+	{
+	if( messLang == c2ps_opPROX.MLANG_GERMAN )
+		return getErrMessGE(errCode, text);
+	else
+		return getErrMessEN(errCode, text);	
+	}
+
+	/**
+	 * buildErrorTree(): 
+	 * @param text = part of the query that contains an error.
+	 * @param errCode
+	 * @param typeDIST
+	 * @param pos
+	 * @return
+	 */
+	
 	private static CommonTree buildErrorTree(String text, int errCode, int typeDIST, int pos) 
 	
 	{
@@ -37,38 +146,8 @@
 	String
 		mess;
 	
-	switch( errCode )
-		{
-	case StatusCodes.ERR_PROX_MEAS_NULL:
-		mess      = String.format("Abstandsoperator an der Stelle '%s' es fehlt eine der folgenden Angaben: w,s,p!", text);
-		errorMes  = new CommonTree(new CommonToken(typeERROR, mess));
-		break;
-	case StatusCodes.ERR_PROX_MEAS_TOOGREAT:
-		mess      = String.format("Abstandsoperator an der Stelle '%s': Bitte nur 1 der folgenden Angaben einsetzen: w,s,p! " +
-							 "Falls Mehrfachangabe erwünscht, müssen diese durch Kommata getrennt werden (z.B.: /+w2,s0).", text);
-		errorMes  = new CommonTree(new CommonToken(typeERROR, mess));
-		break;
-	case StatusCodes.ERR_PROX_VAL_NULL:
-		mess      = String.format("Abstandsoperator an der Stelle '%s': Bitte einen numerischen Wert einsetzen (z.B. /+w5)! ", text);
-		errorMes  = new CommonTree(new CommonToken(typeERROR, mess));
-		break;
-	case StatusCodes.ERR_PROX_VAL_TOOGREAT:
-		mess      = String.format("Abstandsoperator an der Stelle '%s': Bitte nur 1 numerischen Wert einsetzen (z.B. /+w5)! ", text);
-		errorMes  = new CommonTree(new CommonToken(typeERROR, mess));
-		break;
-	case StatusCodes.ERR_PROX_DIR_TOOGREAT:
-		mess      = String.format("Abstandsoperator an der Stelle '%s': Bitte nur 1 Angabe '+' oder '-' oder keine! ", text);
-		errorMes  = new CommonTree(new CommonToken(typeERROR, mess));
-		break;
-	case StatusCodes.ERR_PROX_WRONG_CHARS:
-		mess      = String.format("Abstandsoperator an der Stelle '%s': unbekannte Abstandsoption(en)!", text);
-		errorMes  = new CommonTree(new CommonToken(typeERROR, mess));
-		break;
-	default:
-		mess = String.format("Abstandsoperator an der Stelle '%s': unbekannter Fehler. Korrekte Syntax z.B.: /+w2 oder /w10,s0.", text);
-
-		errorMes  = new CommonTree(new CommonToken(typeERROR, mess));
-		}
+	mess 	 = getErrMess(errCode, messLang, text);
+	errorMes = new CommonTree(new CommonToken(typeERROR, mess));
 	
 	errorTree.addChild(errorNode);
 	errorNode.addChild(errorPos);
diff --git a/src/main/java/de/ids_mannheim/korap/query/serialize/Cosmas2QueryProcessor.java b/src/main/java/de/ids_mannheim/korap/query/serialize/Cosmas2QueryProcessor.java
index a6c7bd9..16af2a3 100644
--- a/src/main/java/de/ids_mannheim/korap/query/serialize/Cosmas2QueryProcessor.java
+++ b/src/main/java/de/ids_mannheim/korap/query/serialize/Cosmas2QueryProcessor.java
@@ -9,6 +9,7 @@
 import de.ids_mannheim.korap.query.object.KoralOperation;
 import de.ids_mannheim.korap.query.object.KoralTermGroupRelation;
 import de.ids_mannheim.korap.query.object.KoralType;
+import de.ids_mannheim.korap.query.parse.cosmas.c2ps_opPROX; 
 import de.ids_mannheim.korap.query.parse.cosmas.c2psLexer;
 import de.ids_mannheim.korap.query.parse.cosmas.c2psParser;
 import de.ids_mannheim.korap.query.serialize.util.Antlr3DescriptiveErrorListener;
@@ -150,7 +151,7 @@
     private boolean reportErrorsinTree(Tree node)
     
     {
-    	final String func = "reportErrorsinTree";
+    	// not used when not debugging: final String func = "reportErrorsinTree";
     	
     	//System.err.printf("Debug: %s: '%s' has %d children.\n",
     	//		func, node.getText(), node.getChildCount());
@@ -178,8 +179,8 @@
     		int
     			errCode = node.getChild(1) != null ? Integer.parseInt(node.getChild(1).getText()) : StatusCodes.ERR_PROX_UNKNOWN; 
     		String
-    			errMess = node.getChild(2) != null ? node.getChild(2).getText() : "Genaue Fehlermeldung nicht auffindbar.";
-    		
+    			errMess = node.getChild(2) != null ? node.getChild(2).getText() : c2ps_opPROX.getErrMess(StatusCodes.UNKNOWN_QUERY_ERROR, "");
+    			
 			ArrayList<Object> 
 				errorSpecs = new ArrayList<Object>();
 			
@@ -1844,9 +1845,6 @@
             org.antlr.runtime.CommonTokenStream tokens =
                     new org.antlr.runtime.CommonTokenStream(lex); // v3
             
-           // System.out.printf("parseCosmasQuery: tokens = %d\n",  tokens.size());
-           // System.out.printf("parseCosmasQuery: tokens = %s\n",  tokens.toString());
-           
             parser = new c2psParser(tokens);
            
             // Use custom error reporters
diff --git a/src/main/java/de/ids_mannheim/korap/query/serialize/QuerySerializer.java b/src/main/java/de/ids_mannheim/korap/query/serialize/QuerySerializer.java
index deaa58e..a51bae1 100644
--- a/src/main/java/de/ids_mannheim/korap/query/serialize/QuerySerializer.java
+++ b/src/main/java/de/ids_mannheim/korap/query/serialize/QuerySerializer.java
@@ -18,8 +18,6 @@
 import de.ids_mannheim.korap.query.serialize.util.KoralObjectGenerator;
 import de.ids_mannheim.korap.query.serialize.util.StatusCodes;
 
-import com.fasterxml.jackson.core.JsonPointer;
-
 /**
  * Main class for Koral, serializes queries from concrete QLs to KoralQuery
  * 
@@ -116,11 +114,9 @@
             queries = new String[] { args[0] };
             ql = args[1];
         }
-        if( args.length >= 3 )
-	        {
-        	if( args[2].compareToIgnoreCase("-show") == 0 )
-	        	bDebug = true;	
-	        }
+
+        if( args.length >= 3 && args[2].compareToIgnoreCase("-show") == 0 )
+        	bDebug = true;	
         
         for (String q : queries) {
             i++;
@@ -153,7 +149,7 @@
      *            'poliqarpplus', 'cqp', 'cosmas2', 'annis' or 'cql'.
      * @throws IOException
      */
-    
+
     public void run (String query, String queryLanguage, boolean bDebug) throws IOException {
 
     	ast.verbose = bDebug; // debugging: 01.09.23/FB
diff --git a/src/main/java/de/ids_mannheim/korap/util/C2RecognitionException.java b/src/main/java/de/ids_mannheim/korap/util/C2RecognitionException.java
index 92ba9ef..358dd0c 100644
--- a/src/main/java/de/ids_mannheim/korap/util/C2RecognitionException.java
+++ b/src/main/java/de/ids_mannheim/korap/util/C2RecognitionException.java
@@ -9,7 +9,6 @@
 
 public final class C2RecognitionException extends RecognitionException {
 
-	private static final boolean DEBUG = false;
 	public String mismatchedToken;
 	
 	public C2RecognitionException(String mismatchedToken)
diff --git a/src/test/java/de/ids_mannheim/korap/test/cosmas2/Cosmas2QueryProcessorTest.java b/src/test/java/de/ids_mannheim/korap/test/cosmas2/Cosmas2QueryProcessorTest.java
index bb4319c..b366594 100644
--- a/src/test/java/de/ids_mannheim/korap/test/cosmas2/Cosmas2QueryProcessorTest.java
+++ b/src/test/java/de/ids_mannheim/korap/test/cosmas2/Cosmas2QueryProcessorTest.java
@@ -513,6 +513,7 @@
 
     @Test
     public void testOPPROX () throws JsonProcessingException, IOException {
+    	
         query = "Sonne /+w1:4 Mond";
         qs.setQuery(query, "cosmas2");
         res = mapper.readTree(qs.toJSON());
@@ -630,31 +631,95 @@
                 .asText());
         assertFalse(res.at("/query/inOrder").asBoolean());
         
-        // 15.01.24/FB: checking syntax error detectiong:
+        // -- check exclude operator -- // 
+        
+        query = "Sonne %-w1:2 Sterne";
+        qs.setQuery(query,  "cosmas2");
+    	res = mapper.readTree(qs.toJSON());
+      	
+    	/*
+    	System.out.printf("Query '%s': returns: '%s'.\n", query, res.toPrettyString()) ;
+    	System.out.printf("[0]: '%s'.\n",  res.at("/query/distances").get(0).get("boundary").toPrettyString());
+    	System.out.printf("@type: '%s'.\n",  res.at("/query/distances").get(0).get("@type").asText());
+    	System.out.printf("exclude: '%s'.\n",  res.at("/query/distances").get(0).get("exclude").asText());
+    	System.out.printf("key: '%s'.\n",  res.at("/query/distances").get(0).get("key").asText());
+    	*/
+    	
+    	assertEquals("cosmas:distance",  res.at("/query/distances").get(0).get("@type").asText());
+    	assertTrue( res.at("/query/distances").get(0).get("exclude").asBoolean());
+    	assertEquals("w", res.at("/query/distances").get(0).get("key").asText());
+    	
+        // 15.01.24/FB: checking syntax error:
         
         query = "Sonne /+w Mond"; // distance value missing.
         qs.setQuery(query, "cosmas2");
         res = mapper.readTree(qs.toJSON());
         
         assertTrue(res.get("errors") != null);
+        //System.out.printf("Query '%s': errors : '%s'.\n", query, res.get("errors").toPrettyString()) ;
+        assertEquals(StatusCodes.ERR_PROX_VAL_NULL, res.get("errors").get(0).get(0).asInt());
         
         query = "Sonne /+2sw Mond"; // 2 distance types instead of 1.
         qs.setQuery(query, "cosmas2");
         res = mapper.readTree(qs.toJSON());
-        
+          
         assertTrue(res.get("errors") != null);
+        //System.out.printf("Query '%s': errors : '%s'.\n", query, res.get("errors").toPrettyString()) ;
+    	assertEquals(StatusCodes.ERR_PROX_MEAS_TOOGREAT, res.get("errors").get(0).get(0).asInt());
         
         query = "Sonne /+2s- Mond"; // 2 distance directions instead of 1.
         qs.setQuery(query, "cosmas2");
         res = mapper.readTree(qs.toJSON());
         
         assertTrue(res.get("errors") != null);
-
+        //System.out.printf("Query '%s': errors : '%s'.\n", query, res.get("errors").toPrettyString()) ;
+    	assertEquals(StatusCodes.ERR_PROX_DIR_TOOGREAT, res.get("errors").get(0).get(0).asInt());
+        
         query = "Sonne /+2s7 Mond"; // 2 distance values instead of 1.
         qs.setQuery(query, "cosmas2");
         res = mapper.readTree(qs.toJSON());
         
         assertTrue(res.get("errors") != null);
+        //System.out.printf("Query '%s': errors : '%s'.\n", query, res.get("errors").toPrettyString()) ;
+    	assertEquals(StatusCodes.ERR_PROX_VAL_TOOGREAT, res.get("errors").get(0).get(0).asInt());
+        
+    	// tests for error messages for unknown proximity options:
+    	// 29.05.24/FB
+    	
+    	query = "ab /+w1:2u,p cd";
+    	qs.setQuery(query,  "cosmas2");
+    	res = mapper.readTree(qs.toJSON());
+    	
+    	assertTrue("Error code expected!",!res.get("errors").isNull());
+    	assertEquals(StatusCodes.ERR_PROX_WRONG_CHARS, res.get("errors").get(0).get(0).asInt());
+    	
+    	query = "ab %-w1:2,2su cd";
+    	qs.setQuery(query,  "cosmas2");
+    	res = mapper.readTree(qs.toJSON());
+
+    	assertTrue("Error code expected!",!res.get("errors").isNull());
+    	assertEquals(StatusCodes.ERR_PROX_WRONG_CHARS, res.get("errors").get(0).get(0).asInt());
+    	
+    	query = "ab /w1:2s cd";
+    	qs.setQuery(query,  "cosmas2");
+    	res = mapper.readTree(qs.toJSON());
+
+      	//System.out.printf("Query '%s': context: '%s'.\n", query, res.get("@context").toPrettyString()) ;
+    	//System.out.printf("Query '%s': errors : '%s'.\n", query, res.get("errors").toPrettyString()) ;
+    	//System.out.printf("Query '%s': errorCode: '%s'.\n", query, res.get("errors").get(0).get(0).toPrettyString()) ;
+    	//System.out.printf("Query '%s': errorText : '%s'.\n", query, res.get("errors").get(0).get(1).toPrettyString()) ;
+    	//System.out.printf("Query '%s': errorPos : '%s'.\n", query, res.get("errors").get(0).get(2).toPrettyString()) ;
+    
+      	assertTrue("Error code expected!", res.get("errors") != null);
+    	assertEquals(StatusCodes.ERR_PROX_MEAS_TOOGREAT, res.get("errors").get(0).get(0).asInt());
+    	
+    	query = "Sonne %-w1:2,+2su Galaxien";
+        qs.setQuery(query,  "cosmas2");
+    	res = mapper.readTree(qs.toJSON());
+
+      	assertTrue("Error code expected!", res.get("errors") != null);
+    	assertEquals(StatusCodes.ERR_PROX_WRONG_CHARS, res.get("errors").get(0).get(0).asInt());
+
     }