diff --git a/oaipmh-core/pom.xml b/oaipmh-core/pom.xml
index a35e202174a236caa520005d021deb2a18075232..1f618bf0ac42ce4e891298d749f9f24075fd4751 100644
--- a/oaipmh-core/pom.xml
+++ b/oaipmh-core/pom.xml
@@ -74,28 +74,22 @@
 			<artifactId>slf4j-api</artifactId>
 			<version>${slf4j.version}</version>
 		</dependency>
-		<!-- <dependency> -->
-		<!-- <groupId>org.slf4j</groupId> -->
-		<!-- <artifactId>jcl-over-slf4j</artifactId> -->
-		<!-- <version>${slf4j.version}</version> -->
-		<!-- <scope>runtime</scope> -->
-		<!-- </dependency> -->
-		<!-- <dependency> -->
-		<!-- <groupId>org.slf4j</groupId> -->
-		<!-- <artifactId>slf4j-log4j12</artifactId> -->
-		<!-- <version>${slf4j.version}</version> -->
-		<!-- <scope>runtime</scope> -->
-		<!-- </dependency> -->
-		<!-- <dependency> -->
-		<!-- <groupId>log4j</groupId> -->
-		<!-- <artifactId>log4j</artifactId> -->
-		<!-- <version>1.2.14</version> -->
-		<!-- </dependency> -->
-		<!-- https://mvnrepository.com/artifact/org.apache.logging.log4j/log4j-core -->
-		<dependency>
-			<groupId>org.apache.logging.log4j</groupId>
-			<artifactId>log4j-core</artifactId>
-			<version>2.14.1</version>
+		<dependency>
+			<groupId>org.slf4j</groupId>
+			<artifactId>jcl-over-slf4j</artifactId>
+			<version>${slf4j.version}</version>
+			<scope>runtime</scope>
+		</dependency>
+		<dependency>
+			<groupId>org.slf4j</groupId>
+			<artifactId>slf4j-log4j12</artifactId>
+			<version>${slf4j.version}</version>
+			<scope>runtime</scope>
+		</dependency>
+		<dependency>
+			<groupId>log4j</groupId>
+			<artifactId>log4j</artifactId>
+			<version>1.2.14</version>
 		</dependency>
 		<dependency>
 			<groupId>org.classicmayan.tools</groupId>
diff --git a/oaipmh-core/src/main/java/info/textgrid/middleware/IdentifierListDelivererDC.java b/oaipmh-core/src/main/java/info/textgrid/middleware/IdentifierListDelivererDC.java
index 34f7d1bb6335715bef0d7a39315f7647e38b7c8f..713847cbd599a5cd985c03769b9edb1aa9d68ea4 100644
--- a/oaipmh-core/src/main/java/info/textgrid/middleware/IdentifierListDelivererDC.java
+++ b/oaipmh-core/src/main/java/info/textgrid/middleware/IdentifierListDelivererDC.java
@@ -37,7 +37,7 @@ import info.textgrid.middleware.oaipmh.ResumptionTokenType;
 
 public class IdentifierListDelivererDC extends IdentifierListDelivererAbstract {
 
-  private static Log logger = LogFactory.getLog(IdentifierListDelivererDC.class);
+  private static Log log = LogFactory.getLog(IdentifierListDelivererDC.class);
 
   private static final int lifeTimeResToken = 100;
   private static final String DH_ES_DIVIDER_CHAR = ".";
@@ -167,12 +167,12 @@ public class IdentifierListDelivererDC extends IdentifierListDelivererAbstract {
     long size = listFurtherValues.getHits().totalHits;
     setResultSize(size);
 
-    logger.info(" ## hits --> " + size);
+    log.info(" ## hits --> " + size);
 
     for (SearchHit hit : listFurtherValues.getHits().getHits()) {
       i++;
 
-      this.logger.info(" ## hit --> " + hit.getId());
+      log.info(" ## hit --> " + hit.getId());
 
       // Handle TextGrid.
       if (this.textgrid) {
@@ -181,9 +181,9 @@ public class IdentifierListDelivererDC extends IdentifierListDelivererAbstract {
         try {
           datestamp = OAIPMHUtilities.convertDateFormat(datestamp).toXMLFormat();
         } catch (ParseException e) {
-          this.logger.error(e.getMessage());
+          log.error(e.getMessage());
         } catch (DatatypeConfigurationException e) {
-          this.logger.error(e.getMessage());
+          log.error(e.getMessage());
         }
         String identifier = hit.getSourceAsMap().get(this.identifierField).toString();
         lit = setListIdentifierHeader(datestamp, identifier, lit, set);
@@ -192,7 +192,7 @@ public class IdentifierListDelivererDC extends IdentifierListDelivererAbstract {
       // Handle DARIAH.
       else if (this.dariah) {
 
-        this.logger.info(" ## dateOfObjectCreation --> " + this.dateOfObjectCreation);
+        log.info(" ## dateOfObjectCreation --> " + this.dateOfObjectCreation);
 
         JSONObject json = new JSONObject(hit.getSourceAsMap());
 
@@ -231,17 +231,17 @@ public class IdentifierListDelivererDC extends IdentifierListDelivererAbstract {
         // Convert datestamp.
         try {
 
-          this.logger.info(" ## datestamp --> " + this.datestamp);
+          log.info(" ## datestamp --> " + this.datestamp);
 
           this.datestamp = OAIPMHUtilities.convertDateFormat(this.datestamp).toXMLFormat();
 
-          this.logger.info(" ## datestamp converted --> " + this.datestamp);
+          log.info(" ## datestamp converted --> " + this.datestamp);
 
         } catch (ParseException e) {
-          this.logger.error(e.getMessage());
+          log.error(e.getMessage());
           // FIXME Go to ERROR state!
         } catch (DatatypeConfigurationException e) {
-          this.logger.error(e.getMessage());
+          log.error(e.getMessage());
           // FIXME Go to ERROR state!
         }
 
@@ -278,7 +278,7 @@ public class IdentifierListDelivererDC extends IdentifierListDelivererAbstract {
           identifier = hit.getSourceAsMap().get(this.identifierField).toString();
         }
 
-        this.logger.info(" ## identifier --> " + identifier);
+        log.info(" ## identifier --> " + identifier);
 
         lit = setListIdentifierHeader(this.datestamp, identifier, lit, set);
       }
diff --git a/oaipmh-core/src/main/java/info/textgrid/middleware/OAIPMHUtilities.java b/oaipmh-core/src/main/java/info/textgrid/middleware/OAIPMHUtilities.java
index 541a91fb4d0fd4dd13db83a1d53e333837e47462..c3accfb67bbfca9342591db916f21a0faf29b203 100644
--- a/oaipmh-core/src/main/java/info/textgrid/middleware/OAIPMHUtilities.java
+++ b/oaipmh-core/src/main/java/info/textgrid/middleware/OAIPMHUtilities.java
@@ -74,7 +74,7 @@ import info.textgrid.middleware.common.TextGridMimetypes;
  */
 public class OAIPMHUtilities {
 
-  private static Log logger = LogFactory.getLog(OAIPMHUtilities.class);
+  private static Log log = LogFactory.getLog(OAIPMHUtilities.class);
 
   // **
   // FINALS
@@ -327,7 +327,7 @@ public class OAIPMHUtilities {
       final String resumptionToken, Map<String, Integer> cursorCollector, final String scrollID,
       final int searchResponseSize, final int i) {
 
-    logger.debug("Creating a ResumptionToken:\n " +
+    log.debug("Creating a ResumptionToken:\n " +
         "CompleteListSize: " + completeListSize + "\n" +
         "ResumptionToken: " + resumptionToken + "\n" +
         "CursorCollector: " + cursorCollector + "\n" +
@@ -500,7 +500,7 @@ public class OAIPMHUtilities {
 
     String fieldResulst = "";
 
-    logger.debug("Inside fieldLoader for field: " + field);
+    log.debug("Inside fieldLoader for field: " + field);
 
     String[] fieldPathForESIndex = field.split("\\.");
     JSONObject singlePath = resultFromGetRequestInES;
diff --git a/oaipmh-core/src/main/java/info/textgrid/middleware/RecordDelivererDC.java b/oaipmh-core/src/main/java/info/textgrid/middleware/RecordDelivererDC.java
index 5aedb3d5a2e1aab258c300bf8d5bbf9e4ddbd69e..0a0cfe692c3986b64c78740659f59799fcfe5e48 100644
--- a/oaipmh-core/src/main/java/info/textgrid/middleware/RecordDelivererDC.java
+++ b/oaipmh-core/src/main/java/info/textgrid/middleware/RecordDelivererDC.java
@@ -3,6 +3,7 @@ package info.textgrid.middleware;
 import java.io.IOException;
 import java.text.ParseException;
 import javax.xml.datatype.DatatypeConfigurationException;
+import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.elasticsearch.action.get.GetResponse;
 import org.elasticsearch.common.Strings;
@@ -59,7 +60,7 @@ public class RecordDelivererDC extends RecordDelivererAbstract {
   private String[] titleList;
   private String[] typeList;
 
-  private static org.apache.commons.logging.Log log = LogFactory.getLog(RecordDelivererDC.class);
+  private static Log log = LogFactory.getLog(RecordDelivererDC.class);
   private OAI_ESClient oaiEsClient;
 
   /**
@@ -109,14 +110,14 @@ public class RecordDelivererDC extends RecordDelivererAbstract {
         dublinCoreBuilder = putContentIntoDCFieldLists(esResultObject);
         JSONObject json = new JSONObject(esResultObject.getSourceAsMap());
         identifier = OAIPMHUtilities.fieldLoader(json, this.identifierField);
-        //identifier = esResultObject.getSourceAsMap().get(this.identifierField).toString();
+        // identifier = esResultObject.getSourceAsMap().get(this.identifierField).toString();
         String dateOfCreation = "NO_DATE_SET!";
-               
+
         if (OAIPMHUtilities.fieldLoader(json, this.dateOfObjectCreation) != null) {
           try {
             dateOfCreation = OAIPMHUtilities
                 .convertDateFormat(
-                		OAIPMHUtilities.fieldLoader(json, this.dateOfObjectCreation).toString())
+                    OAIPMHUtilities.fieldLoader(json, this.dateOfObjectCreation).toString())
                 .toXMLFormat();
           } catch (ParseException e) {
             // TODO Auto-generated catch block
@@ -128,9 +129,9 @@ public class RecordDelivererDC extends RecordDelivererAbstract {
           record.setMetadata(dublinCoreBuilder.getDC());
         }
         String setSpec = OAIPMHUtilities.fieldLoader(json, this.identifierField);
-        //String setSpec =
-            //DublinCoreFieldLoader.fillList(esResultObject, DARIAHConstants.IDENTIFIER_LIST).get(0);
-        
+        // String setSpec =
+        // DublinCoreFieldLoader.fillList(esResultObject, DARIAHConstants.IDENTIFIER_LIST).get(0);
+
         setRecordHeader(dateOfCreation, identifier, record, dublinCoreBuilder, setSpec);
       }
 
@@ -270,7 +271,7 @@ public class RecordDelivererDC extends RecordDelivererAbstract {
       throws ParseException, DatatypeConfigurationException {
 
     DublinCoreBuilder result = new DublinCoreBuilder();
-    
+
     // Set DublinCore lists with content from elastic search results due to configuration.
     result.setContributor(
         DublinCoreFieldLoader.fillList(responseWorkValues, this.contributorList));
@@ -281,8 +282,9 @@ public class RecordDelivererDC extends RecordDelivererAbstract {
         DublinCoreFieldLoader.fillList(responseWorkValues, this.descriptionList));
     result.setFormat(DublinCoreFieldLoader.fillList(responseWorkValues, this.formatList));
     result.setIdentifier(
-    	OAIPMHUtilities.fieldLoader(new JSONObject(responseWorkValues.getSourceAsMap()), this.identifierList));
-    
+        OAIPMHUtilities.fieldLoader(new JSONObject(responseWorkValues.getSourceAsMap()),
+            this.identifierList));
+
     result.setLanguage(DublinCoreFieldLoader.fillList(responseWorkValues, this.languageList));
     result.setPublisher(DublinCoreFieldLoader.fillList(responseWorkValues, this.publisherList));
     result.setRelation(
diff --git a/oaipmh-core/src/main/java/info/textgrid/middleware/SetDeliverer.java b/oaipmh-core/src/main/java/info/textgrid/middleware/SetDeliverer.java
index 64f4017b64f6f8af636f163572cb981c14785538..8a12aa639ff0c6833e6d209bcd71a3b374a1e5da 100644
--- a/oaipmh-core/src/main/java/info/textgrid/middleware/SetDeliverer.java
+++ b/oaipmh-core/src/main/java/info/textgrid/middleware/SetDeliverer.java
@@ -27,7 +27,7 @@ import info.textgrid.middleware.oaipmh.SetType;
  */
 public class SetDeliverer {
 
-  private static Log logger = LogFactory.getLog(SetDeliverer.class);
+  private static Log log = LogFactory.getLog(SetDeliverer.class);
 
   private static final int DH_SIZE = 100000;
 
@@ -138,19 +138,18 @@ public class SetDeliverer {
 
     request.source(searchSourceBuilder);
 
-    logger.info(" ## SetDeliverer() request --> " + request);
+    log.info(" ## SetDeliverer() request --> " + request);
 
     // Get items with TG or DH request.
     SearchResponse getRecordListItems = null;
     try {
       getRecordListItems = OAI_ESClient.getEsClient().search(request, RequestOptions.DEFAULT);
 
-      logger
-          .info(" ## SetDeliverer() list item count --> " + getRecordListItems.getHits().totalHits);
+      log.info(" ## SetDeliverer() list item count --> " + getRecordListItems.getHits().totalHits);
 
     } catch (IOException e) {
       // TODO Auto-generated catch block
-      logger.error(e.getMessage());
+      log.error(e.getMessage());
       e.printStackTrace();
     }
 
@@ -192,7 +191,7 @@ public class SetDeliverer {
 
           String name = entry.getKey();
 
-          logger.info(" ## entry key --> " + entry.getKey());
+          log.info(" ## entry key --> " + entry.getKey());
 
           if (name.equals(DH_COLLECTION_FILTER_NAME)) {
             Filter filterCollection =
@@ -203,16 +202,16 @@ public class SetDeliverer {
               // Divide ID and title.
               String combined = b.getKeyAsString();
 
-              logger.info(" ## combined --> " + combined);
+              log.info(" ## combined --> " + combined);
 
               int indexOf = combined.indexOf(DH_FIELD_DIVIDER);
               String id = combined.substring(0, indexOf);
 
-              logger.info(" ## id --> " + id);
+              log.info(" ## id --> " + id);
 
               String title = combined.substring(indexOf + 1);
 
-              logger.info(" ## title --> " + title);
+              log.info(" ## title --> " + title);
 
               // Set set.
               SetType newSet = new SetType();