diff --git a/defaults/solr.keys.list b/defaults/solr.keys.list
index 1739252553..78c51beb32 100644
--- a/defaults/solr.keys.list
+++ b/defaults/solr.keys.list
@@ -65,6 +65,9 @@ httpstatus_i
 ## redirect url if the error code is 299 < httpstatus_i < 310
 #httpstatus_redirect_s
 
+## number of unique http references; used for ranking
+references_i
+
 ### optional but highly recommended values, part of the index distribution process
 
 ## time when resource was loaded
diff --git a/htroot/gsa/searchresult.java b/htroot/gsa/searchresult.java
index 14a3f92786..7797426583 100644
--- a/htroot/gsa/searchresult.java
+++ b/htroot/gsa/searchresult.java
@@ -119,8 +119,8 @@ public static serverObjects respond(final RequestHeader header, final serverObje
         post.put(CommonParams.Q, solrQ.toString());
         post.put(CommonParams.ROWS, post.remove("num"));
         post.put(CommonParams.ROWS, Math.min(post.getInt(CommonParams.ROWS, 10), (authenticated) ? 5000 : 100));
-        float f = Boost.RANKING.get(YaCySchema.fuzzy_signature_unique_b);
-        post.put("bq", YaCySchema.fuzzy_signature_unique_b.getSolrFieldName() + ":true^" + Float.toString(f)); // a boost query that moves double content to the back
+        post.put("bq", Boost.RANKING.getBoostQuery()); // a boost query that moves double content to the back
+        post.put("bf", Boost.RANKING.getBoostFunction()); // a boost function extension
         post.put(CommonParams.FL,
                 YaCySchema.content_type.getSolrFieldName() + ',' +
                 YaCySchema.id.getSolrFieldName() + ',' +
diff --git a/source/net/yacy/cora/federate/solr/Boost.java b/source/net/yacy/cora/federate/solr/Boost.java
index c6a8c3e181..0348e1c3c2 100644
--- a/source/net/yacy/cora/federate/solr/Boost.java
+++ b/source/net/yacy/cora/federate/solr/Boost.java
@@ -46,7 +46,8 @@ public class Boost extends LinkedHashMap<YaCySchema, Float> {
         YaCySchema.description,
         YaCySchema.keywords,
         YaCySchema.text_t,
-        YaCySchema.synonyms_sxt
+        YaCySchema.synonyms_sxt,
+        YaCySchema.references_i
     };
     
     // for minTokenLen = 2 the quantRate value should not be below 0.24; for minTokenLen = 3 the quantRate value must be not below 0.5!
@@ -118,4 +119,20 @@ public int getMinTokenLen() {
         return minTokenLen;
     }
 
+    /**
+     * produce a string that can be added as a 'boost query' at the bq-attribute
+     * @return
+     */
+    public String getBoostQuery() {
+        return YaCySchema.fuzzy_signature_unique_b.getSolrFieldName() + ":true^" + Float.toString(this.get(YaCySchema.fuzzy_signature_unique_b));
+    }
+    
+    /**
+     * produce a boost function
+     * @return
+     */
+    public String getBoostFunction() {
+        return "div(add(1,references_i),pow(add(1,inboundlinkscount_i),1.6))^0.4";
+    }
+    
 }
diff --git a/source/net/yacy/cora/federate/solr/YaCySchema.java b/source/net/yacy/cora/federate/solr/YaCySchema.java
index 857bc3be35..2436f53522 100644
--- a/source/net/yacy/cora/federate/solr/YaCySchema.java
+++ b/source/net/yacy/cora/federate/solr/YaCySchema.java
@@ -47,6 +47,7 @@ public enum YaCySchema implements Schema {
     failtype_s(SolrType.string, true, true, false, "fail type if a page was not loaded. This field is either empty, 'excl' or 'fail'"),
     httpstatus_i(SolrType.num_integer, true, true, false, "html status return code (i.e. \"200\" for ok), -1 if not loaded"),
     httpstatus_redirect_s(SolrType.num_integer, true, true, false, "html status return code (i.e. \"200\" for ok), -1 if not loaded"),
+    references_i(SolrType.num_integer, true, true, false, "number of unique http references; used for ranking"),
 
     // optional but recommended, part of index distribution
     load_date_dt(SolrType.date, true, true, false, "time when resource was loaded"),
diff --git a/source/net/yacy/search/index/Segment.java b/source/net/yacy/search/index/Segment.java
index f6ef24d750..c7fb42215e 100644
--- a/source/net/yacy/search/index/Segment.java
+++ b/source/net/yacy/search/index/Segment.java
@@ -383,6 +383,13 @@ public SolrInputDocument storeDocument(
             }
         }
         
+        // ENRICH DOCUMENT WITH RANKING INFORMATION
+        if (this.urlCitationIndex != null && this.fulltext.getSolrScheme().contains(YaCySchema.references_i)) {
+            int references = this.urlCitationIndex.count(url.hash());
+            if (references > 0) solrInputDoc.setField(YaCySchema.references_i.getSolrFieldName(), references);
+        }
+        
+        
         // STORE TO SOLR
         String error = null;
         tryloop: for (int i = 0; i < 20; i++) {
diff --git a/source/net/yacy/search/query/QueryParams.java b/source/net/yacy/search/query/QueryParams.java
index 00afbc9f06..1bd921ee9a 100644
--- a/source/net/yacy/search/query/QueryParams.java
+++ b/source/net/yacy/search/query/QueryParams.java
@@ -428,8 +428,8 @@ public SolrQuery solrQuery() {
         // construct query
         final SolrQuery params = new SolrQuery();
         params.setParam("defType", "edismax");
-        float f = Boost.RANKING.get(YaCySchema.fuzzy_signature_unique_b);
-        params.setParam("bq", YaCySchema.fuzzy_signature_unique_b.getSolrFieldName() + ":true^" + Float.toString(f)); // a boost query that moves double content to the back
+        params.setParam("bq", Boost.RANKING.getBoostQuery()); // a boost query that moves double content to the back
+        params.setParam("bf", Boost.RANKING.getBoostFunction()); // a boost function extension
         params.setStart(this.offset);
         params.setRows(this.itemsPerPage);
         params.setFacet(false);