Hi gang! There's a June 2000 Stanford University doctoral thesis pertinent to ZigZag available online at http://graphics.stanford.edu/papers/munzner_thesis/index.html#toc It's by Tamara Munzner. Her Stanford Web page is http://graphics.stanford.edu/~munzner/ -- Jan -- Jan Theodore Galkowski (o°) codingwizard@xxxxxxxxxxxxxx http://www.algebraist.com/