Affiliation: | 1. Department of Mathematics, Michigan State University, East Lansing, MI 48824-1027, USA;2. KU Leuven, Departement Wiskunde, Celestijnenlaan 200B – Box 2400, BE-3001 Leuven, Belgium;3. Université de Valenciennes, Lamath, ISTV2, Campus du Mont Houy, 59313 Valenciennes, Cedex 9, France |