Affiliation: | 1. Dipartimento di Matematica e Informatica, Università degli Studi di Cagliari, Via Ospedale 72, 09124, Cagliari, Italy 2. Department of Mathematics, Michigan State University, East Lansing, MI, 48824-1027, USA 3. Laboratoire de Mathématiques, Informatique et Applications, Université de Haute Alsace, 4, Rue des Frères Lumière, 68093, Mulhouse Cédex, France
|