Affiliation: | 1. AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland;2. Alfréd Rényi Institute of Mathematics, Hungarian Academy of Sciences, P.O.B. 127, H-1364 Budapest, Hungary;3. Computer Science and Systems Technology, University of Pannonia, H-8200 Veszprém, Egyetem u. 10, Hungary |