/// <summary>
        /// Called whenever a relationship of type ReferenceRSNodeReferencesReferenceNode is added and
        /// the element hosted by this model is the source.
        /// </summary>
        /// <param name="args"></param>
        private void OnReferenceNodeAdded(ElementAddedEventArgs args)
        {
            ReferenceRSNodeReferencesReferenceNode con = args.ModelElement as ReferenceRSNodeReferencesReferenceNode;

            if (con != null)
            {
                AddReferenceNode(con.ReferenceNode);
            }
        }