private Object handleRefn(Object tos) {
      if (tos instanceof PersonFamilyCommonContainer) {
         return new FieldRef(tos, "ReferenceNumber");
      }
      else if (tos instanceof Source && ((Source)tos).getReferenceNumber() == null) {
         return new FieldRef(tos, "ReferenceNumber");
      }
      return null;
   }