diff --git a/src/main/java/lu/jpt/csparqltest/Main.java b/src/main/java/lu/jpt/csparqltest/Main.java
index 06a1794..d48d8a3 100644
--- a/src/main/java/lu/jpt/csparqltest/Main.java
+++ b/src/main/java/lu/jpt/csparqltest/Main.java
@@ -148,14 +148,11 @@ public class Main {
 				+ " BIND(f:timestamp(?a,rdf:type,<http://example.org/type/A>) AS ?tsa) "
 				+ " BIND(f:timestamp(?c,rdf:type,<http://example.org/type/C>) AS ?tsc) "
 				+ " FILTER(?tsa < ?tsc) "
-				+ " OPTIONAL {"
+				+ " FILTER NOT EXISTS { "
 				+ "  ?b a <http://example.org/type/B> . "
 				+ "  BIND(f:timestamp(?b,rdf:type,<http://example.org/type/B>) AS ?tsb) "
-				+ "  FILTER(?tsb < ?tsa || ?tsc < ?tsb)"
+				+ "  FILTER(?tsa < ?tsb && ?tsb < ?tsc)"
 				+ " } "
-				//+ " BIND(BOUND(?b) AS ?bbound) "
-				//+ " BIND(?tsa < ?tsb AS ?abeforeb) "
-				//+ " BIND(?tsb < ?tsc AS ?bbeforec) "
 				+ "}";
 	}