Affiliation: | 1. Institute for Software Technology, University of Technology, Graz, Austria;2. Instituto de Matemáticas, Universidad Nacional Autónoma de México, D.F. México, México;1. Institute of Math. Sciences, IV Cross Road, Taramani, Chennai 600 113, India;2. School of Comp. Science, Simon Fraser University, Burnaby, Canada V5A 1S6;3. DIMAP and Math. Institute, University of Warwick, Coventry CV4 7AL, UK |