diff --git a/src/main/java/eu/dnetlib/dhp/schema/common/ModelConstants.java b/src/main/java/eu/dnetlib/dhp/schema/common/ModelConstants.java
index 44b3755..9ca5a6c 100644
--- a/src/main/java/eu/dnetlib/dhp/schema/common/ModelConstants.java
+++ b/src/main/java/eu/dnetlib/dhp/schema/common/ModelConstants.java
@@ -141,6 +141,8 @@ public class ModelConstants {
 
 	public static final String SIMILARITY = "similarity"; // subreltype
 	public static final String IS_SIMILAR_TO = "isSimilarTo";
+	public static final String IS_AMONG_TOP_N_SIMILAR_DOCS = "isAmongTopNSimilarDocuments";
+	public static final String HAS_AMONG_TOP_N_SIMILAR_DOCS = "hasAmongTopNSimilarDocuments";
 
 	public static final String IS_DIFFERENT_FROM = "isDifferentFrom";