Is there a name for the operation which takes one graph to another, such that the points of the new graph are the edges of the original graph, and there is an edge between two such points if their originating edges shared a point? I.e., each edge becomes a point, and a point with valence n becomes C(n,2) edges. Franklin T. Adams-Watters ________________________________________________________________________ Check Out the new free AIM(R) Mail -- 2 GB of storage and industry-leading spam and email virus protection.