+ * Get the number of nodes of cells included to the group
+ * For a nodal group returns the same value as Size() function
+ */
+ long GetNumberOfNodes();
+
+ /*!
+ * Get IDs of nodes of cells included to the group
+ * For a nodal group returns result of GetListOfID() function
+ */
+ long_array GetNodeIDs();
+
+ /*!
+ * Return true if GetNumberOfNodes() won't take a long time for computation