This field has few, if any, practitioners to date. ---- ''You might be surprised. I count therefore I am.'' See http://www.angelfire.com/mn/psychomath/ or http://www.naturalmath.com/jokes/ ---- wonderful, thank you! ---- Do system builders suffer from an irrational binary bias? See http://www.americanscientist.org/template/AssetDetail/assetid/14405. -- dubya