Affiliation: | 1. Department of Mathematics, The University of Western Ontario, London, Ontario, N6A 5B7 Canada;2. Institute of Mathematics, Faculty of Mathematics and Computer Science, Jagiellonian University, ul. ?ojasiewicza 6, 30-348 Kraków, Poland;3. AGH University of Science and Technology, Faculty of Applied Mathematics, al. A. Mickiewicza 30, 30-059 Krakow, Poland |