W. Barth, M. Jünger, P. Mutzel:
"Simple and Efficient Bilayer Cross Counting";
in: "Journal of Graph Algorithms and Applications", R. Tamassia, I. Tollis, G. Liotta (ed.); World Scientific, 2004, 16 pages.
http://aleph.ub.tuwien.ac.at/F?base=tuw01&func=find-c&ccl_term=AC04968662