diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/common/ModelConstants.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/common/ModelConstants.java
index e32dd10fa9..6db3828235 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/common/ModelConstants.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/common/ModelConstants.java
@@ -34,6 +34,13 @@ public class ModelConstants {
 	public static final String IS_PART_OF = "IsPartOf";
 	public static final String HAS_PARTS = "HasParts";
 	public static final String RELATIONSHIP = "relationship";
+	public static final String CITATION = "citation";
+	public static final String CITES = "cites";
+	public static final String IS_CITED_BY = "IsCitedBy";
+	public static final String REVIEW = "review";
+	public static final String REVIEWS = "reviews";
+	public static final String IS_REVIEWED_BY = "IsReviewedBy";
+
 
 	public static final String RESULT_PROJECT = "resultProject";
 	public static final String OUTCOME = "outcome";