Affiliation: | a Faculty of Mathematics and Computer Science, Jagiellonian University, Institute of Computer Science, ul. Stanis?awa ?ojasiewicza 6, 30348 Krakow, Poland b Laboratoire de Mathématiques, Physique et Systèmes, Université de Perpignan, 52 Avenue Paul Alduy, 66860 Perpignan, France |