diff --git a/Interfaces/IXBaseReferencedProvider.cs b/Interfaces/IXBaseReferencedProvider.cs
index 20b9819..7d6366b 100644
--- a/Interfaces/IXBaseReferencedProvider.cs
+++ b/Interfaces/IXBaseReferencedProvider.cs
@@ -23,11 +23,6 @@ namespace xDataService.Interfaces
         string Provider { get; }
         #endregion
 
-        //
-        #region Identifier ...
-        Task<int> LastIndex(TKey providedForId);
-        #endregion
-
         //
         #region Referenced Actions ...
         /// <summary>
@@ -48,6 +43,13 @@ namespace xDataService.Interfaces
         /// <returns></returns>
         Task<IEnumerable<TModel>> GetAllReferences(TKey providedForId);
 
+        /// <summary>
+        /// Count References ...
+        /// </summary>
+        /// <param name="providedForId"></param>
+        /// <returns></returns>
+        Task<int> CountReferences(TKey providedForId);
+
         /// <summary>
         /// Retrieve References of Specific Provided ID as Query ...
         /// </summary>
@@ -69,7 +71,6 @@ namespace xDataService.Interfaces
         Task<bool> AddReference(
             TModel model,
             TKey providedForId,
-            int forIndex = 0,
             string connectionId = null
         );
 
@@ -97,7 +98,6 @@ namespace xDataService.Interfaces
         Task<bool> RemoveReference(
             TModel model,
             TKey providedForId,
-            int? forIndex = null,
             string connectionId = null
         );