Affiliation: | aFaculty of Informatics, University of Ulster, Magee College, Londonderry BT48 7JL, Northern Ireland, United Kingdom;bDepartment of Statistics, Box 354322, University of Washington, Seattle, WA 98195-4322, USA;cMathSoft Inc., 1700 Westlake Avenue N., Suite 500, Seattle, WA 98109, USA |