diff --git a/dhp-common/pom.xml b/dhp-common/pom.xml
index 4416bd4ff..a9fb39ea0 100644
--- a/dhp-common/pom.xml
+++ b/dhp-common/pom.xml
@@ -46,6 +46,18 @@
 			<groupId>net.sf.saxon</groupId>
 			<artifactId>Saxon-HE</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.slf4j</groupId>
+			<artifactId>jcl-over-slf4j</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.apache.cxf</groupId>
+			<artifactId>cxf-rt-transports-http</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>eu.dnetlib</groupId>
+			<artifactId>cnr-rmi-api</artifactId>
+		</dependency>
 	</dependencies>
 
 </project>
diff --git a/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/graph/utils/ISLookupClientFactory.java b/dhp-common/src/main/java/eu/dnetlib/dhp/utils/ISLookupClientFactory.java
similarity index 96%
rename from dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/graph/utils/ISLookupClientFactory.java
rename to dhp-common/src/main/java/eu/dnetlib/dhp/utils/ISLookupClientFactory.java
index d87f29452..c74cf3c11 100644
--- a/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/graph/utils/ISLookupClientFactory.java
+++ b/dhp-common/src/main/java/eu/dnetlib/dhp/utils/ISLookupClientFactory.java
@@ -1,4 +1,4 @@
-package eu.dnetlib.dhp.graph.utils;
+package eu.dnetlib.dhp.utils;
 
 import eu.dnetlib.enabling.is.lookup.rmi.ISLookUpService;
 import org.apache.commons.logging.Log;
diff --git a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Relation.java b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Relation.java
index 5cf0883be..d404981f4 100644
--- a/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Relation.java
+++ b/dhp-schemas/src/main/java/eu/dnetlib/dhp/schema/oaf/Relation.java
@@ -1,6 +1,11 @@
 package eu.dnetlib.dhp.schema.oaf;
 
+import org.junit.Assert;
+
+import java.util.ArrayList;
 import java.util.List;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 public class Relation extends Oaf {
 
@@ -14,7 +19,7 @@ public class Relation extends Oaf {
 
     private String target;
 
-    private List<KeyValue> collectedFrom;
+    private List<KeyValue> collectedFrom = new ArrayList<>();
 
     public String getRelType() {
         return relType;
@@ -63,4 +68,19 @@ public class Relation extends Oaf {
     public void setCollectedFrom(List<KeyValue> collectedFrom) {
         this.collectedFrom = collectedFrom;
     }
+
+    public void mergeFrom(final Relation r) {
+        Assert.assertEquals("source ids must be equal", getSource(), r.getSource());
+        Assert.assertEquals("target ids must be equal", getTarget(), r.getTarget());
+        Assert.assertEquals("relType(s) must be equal", getRelType(), r.getRelType());
+        Assert.assertEquals("subRelType(s) must be equal", getSubRelType(), r.getSubRelType());
+        Assert.assertEquals("relClass(es) must be equal", getRelClass(), r.getRelClass());
+        setCollectedFrom(
+            Stream.concat(
+                    getCollectedFrom().stream(),
+                    r.getCollectedFrom().stream())
+                .distinct() // relies on KeyValue.equals
+                .collect(Collectors.toList()));
+    }
+
 }
diff --git a/dhp-workflows/dhp-graph-provision/pom.xml b/dhp-workflows/dhp-graph-provision/pom.xml
index f74c9b666..ac4e01d21 100644
--- a/dhp-workflows/dhp-graph-provision/pom.xml
+++ b/dhp-workflows/dhp-graph-provision/pom.xml
@@ -66,14 +66,6 @@
             <artifactId>zookeeper</artifactId>
         </dependency>
 
-        <dependency>
-            <groupId>org.apache.cxf</groupId>
-            <artifactId>cxf-rt-transports-http</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>eu.dnetlib</groupId>
-            <artifactId>cnr-rmi-api</artifactId>
-        </dependency>
 
         <dependency>
             <groupId>eu.dnetlib.dhp</groupId>
diff --git a/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/graph/SparkXmlIndexingJob.java b/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/graph/SparkXmlIndexingJob.java
index 2775d93b4..63ff8fb31 100644
--- a/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/graph/SparkXmlIndexingJob.java
+++ b/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/graph/SparkXmlIndexingJob.java
@@ -2,8 +2,8 @@ package eu.dnetlib.dhp.graph;
 
 import com.lucidworks.spark.util.SolrSupport;
 import eu.dnetlib.dhp.application.ArgumentApplicationParser;
-import eu.dnetlib.dhp.graph.utils.ISLookupClientFactory;
 import eu.dnetlib.dhp.graph.utils.StreamingInputDocumentFactory;
+import eu.dnetlib.dhp.utils.ISLookupClientFactory;
 import eu.dnetlib.dhp.utils.saxon.SaxonTransformerFactory;
 import eu.dnetlib.enabling.is.lookup.rmi.ISLookUpDocumentNotFoundException;
 import eu.dnetlib.enabling.is.lookup.rmi.ISLookUpException;
diff --git a/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/graph/utils/ContextMapper.java b/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/graph/utils/ContextMapper.java
index 0c3a481d0..ad9e7dfad 100644
--- a/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/graph/utils/ContextMapper.java
+++ b/dhp-workflows/dhp-graph-provision/src/main/java/eu/dnetlib/dhp/graph/utils/ContextMapper.java
@@ -1,6 +1,7 @@
 package eu.dnetlib.dhp.graph.utils;
 
 import com.google.common.base.Joiner;
+import eu.dnetlib.dhp.utils.ISLookupClientFactory;
 import eu.dnetlib.enabling.is.lookup.rmi.ISLookUpException;
 import eu.dnetlib.enabling.is.lookup.rmi.ISLookUpService;
 import org.dom4j.Document;
diff --git a/pom.xml b/pom.xml
index 7f5e1e3dc..faed1db35 100644
--- a/pom.xml
+++ b/pom.xml
@@ -129,6 +129,13 @@
 				<scope>provided</scope>
 			</dependency>
 
+			<dependency>
+				<groupId>org.slf4j</groupId>
+				<artifactId>jcl-over-slf4j</artifactId>
+				<version>1.7.25</version>
+				<scope>provided</scope>
+			</dependency>
+
 			<dependency>
 				<groupId>org.apache.commons</groupId>
 				<artifactId>commons-lang3</artifactId>