His site doesn't mention it, and google doesn't turn up anything for the query buium "number derivative" Any idea which papers? Other key words? John McKay wrote:

Alexandru Buium (Univ. New Maxico Albuqquerque) invented such a thing. See his papers..

John

-- Mike Stay staym@clear.net.nz http://www.cs.auckland.ac.nz/~msta039