Institution: | 1. Département de mathématiques, Université de Poitiers, Téléport 2–BP 30179, 86962 Futuroscope Chasseneuil Cedex, France;2. Department of Mathematics-0112, University of California at San Diego, La Jolla, CA 92093-0112, USA;3. Mathematics Laboratory, University of Luxembourg, 162A, Avenue de la Faïencerie, 1511 Luxembourg, Luxembourg |