diff --git a/src/main/java/eu/dnetlib/dhp/schema/oaf/Result.java b/src/main/java/eu/dnetlib/dhp/schema/oaf/Result.java
index 9ede797..9d1f52c 100644
--- a/src/main/java/eu/dnetlib/dhp/schema/oaf/Result.java
+++ b/src/main/java/eu/dnetlib/dhp/schema/oaf/Result.java
@@ -5,10 +5,12 @@ import java.io.Serializable;
 import java.util.*;
 import java.util.stream.Collectors;
 
+import org.apache.commons.lang3.tuple.ImmutablePair;
+import org.apache.commons.lang3.tuple.Pair;
+
 import eu.dnetlib.dhp.schema.common.AccessRightComparator;
 import eu.dnetlib.dhp.schema.common.ModelConstants;
 import eu.dnetlib.dhp.schema.oaf.utils.CleaningFunctions;
-import scala.Tuple2;
 
 /**
  * The type Result.
@@ -571,19 +573,21 @@ public class Result extends OafEntity implements Serializable {
 	 * @return the result map
 	 */
 	public static Map<String, Instance> toInstanceMap(final List<Instance> ri) {
+
+
 		return ri
 				.stream()
 				.filter(i -> i.getPid() != null || i.getAlternateIdentifier() != null)
 				.flatMap(i -> {
-					final List<Tuple2<String, Instance>> result = new ArrayList<>();
+					final List<Pair<String, Instance>> result = new ArrayList<>();
 					if (i.getPid() != null)
-						i.getPid().stream().filter(Result::validPid).forEach(p -> result.add(new Tuple2<>(extractKeyFromPid(p), i)));
+						i.getPid().stream().filter(Result::validPid).forEach(p -> result.add(new ImmutablePair<>(extractKeyFromPid(p), i)));
 					if (i.getAlternateIdentifier() != null)
-						i.getAlternateIdentifier().stream().filter(Result::validPid).forEach(p -> result.add(new Tuple2<>(extractKeyFromPid(p), i)));
+						i.getAlternateIdentifier().stream().filter(Result::validPid).forEach(p -> result.add(new ImmutablePair<>(extractKeyFromPid(p), i)));
 					return result.stream();
 				}).collect(Collectors.toMap(
-						Tuple2::_1,
-						Tuple2::_2,
+						Pair::getLeft,
+						Pair::getRight,
 						(a, b) -> a
 				));
 	}
diff --git a/src/test/java/eu/dnetlib/dhp/schema/oaf/MergeTest.java b/src/test/java/eu/dnetlib/dhp/schema/oaf/MergeTest.java
index 6e335e0..69af8e3 100644
--- a/src/test/java/eu/dnetlib/dhp/schema/oaf/MergeTest.java
+++ b/src/test/java/eu/dnetlib/dhp/schema/oaf/MergeTest.java
@@ -3,7 +3,6 @@ package eu.dnetlib.dhp.schema.oaf;
 
 import static org.junit.jupiter.api.Assertions.*;
 
-
 import java.io.IOException;
 import java.io.InputStream;
 import java.time.format.DateTimeParseException;
@@ -12,12 +11,12 @@ import java.util.List;
 import java.util.Objects;
 import java.util.stream.Collectors;
 
-
-import com.fasterxml.jackson.databind.ObjectMapper;
 import org.apache.commons.io.IOUtils;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
+import com.fasterxml.jackson.databind.ObjectMapper;
+
 /**
  * The type Merge test.
  */