diff --git a/src/main/java/de/ids_mannheim/korap/query/serialize/MetaQuerySerializer.java b/src/main/java/de/ids_mannheim/korap/query/serialize/MetaQuerySerializer.java
index 8088ecc..17b6392 100644
--- a/src/main/java/de/ids_mannheim/korap/query/serialize/MetaQuerySerializer.java
+++ b/src/main/java/de/ids_mannheim/korap/query/serialize/MetaQuerySerializer.java
@@ -65,7 +65,7 @@
     // only handles AND relation between query attributes and values!
     // value pair : pubdate=<date>, pubPlace=<place>, etc.
     public List serializeQueries(Map<String, String> queries, TYPE type) {
-        boolean extend, single = true;
+        boolean extend, single = true; //single = true;
         boolean multypes = queries.keySet().size() > 1;
         List<Map> metavalue;
         String def_key = null;
@@ -150,7 +150,6 @@
 
 
         // todo: missing: - takes only one resource, but resources can be chained!
-        // only filters, no extension
         if (single) {
             if (extend)
                 metavalue = Arrays.asList(types.createMetaExtend((Map) value.get(0)));
diff --git a/src/main/java/de/ids_mannheim/korap/query/serialize/MetaTypes.java b/src/main/java/de/ids_mannheim/korap/query/serialize/MetaTypes.java
index fcabf20..125ec1c 100644
--- a/src/main/java/de/ids_mannheim/korap/query/serialize/MetaTypes.java
+++ b/src/main/java/de/ids_mannheim/korap/query/serialize/MetaTypes.java
@@ -31,7 +31,7 @@
         Map kgroup = new LinkedHashMap<>();
         kgroup.put("@type", "korap:group");
         if (field != null)
-            kgroup.put("field", "korap:field#" + field);
+            kgroup.put("@field", "korap:field#" + field);
         kgroup.put("relation", relation);
         kgroup.put("operands", terms);
         return kgroup;
@@ -43,9 +43,9 @@
             type = "korap:term";
         term.put("@type", type);
         if (field != null)
-            term.put("field", "korap:field#" + field);
+            term.put("@field", "korap:field#" + field);
         if (subtype != null)
-            term.put("subtype", "korap:value#" + subtype);
+            term.put("@subtype", "korap:value#" + subtype);
         term.put("@value", value);
         return term;
     }