Affiliation: | 1. Université catholique de Louvain, Institut de Recherche en Mathématique et Physique, 1348 Louvain-la-Neuve, Belgium;2. Università degli Studi di Padova, Dipartimento di Matematica “Tullio Levi-Civita”, 35121 Padova, Italy;1. Dipartimento di Matematica e Applicazioni ‘‘Renato Caccioppoli’’, Università degli Studi di Napoli Federico II, Via Cintia, Complesso Universitario Monte Sant''Angelo, 80126 Napoli, Italy;2. Facultat de Matemàtiques i Informàtica, Universitat de Barcelona, Gran Via des les Corts Catalanes 585, 08007 Barcelona, Spain;3. Department of Mathematics, Pedagogical University of Cracow, Podchora??ych 2, PL-30-084 Kraków, Poland;4. Institute of Mathematics, Polish Academy of Sciences, ?niadeckich 8, PL-00-656 Warszawa, Poland;1. Departament de Matemàtiques, Universitat Politècnica de Catalunya, Edifici Omega, Jordi Girona, 1-3, 08034 Barcelona, Spain;2. Charles University, Faculty of Mathematics and Physics, Department of Algebra, Sokolovska 83, 18600 Praha 8, Czech Republic |