Affiliation: | 1. Department of Mathematics, University of West Bohemia; Centre of Excellence ITI-Institute for Theoretical Computer Science, Charles University; European Centre of Excellence NTIS-New Technologies for the Information Society, P.O. Box 314, 306 14 Pilsen, Czech Republic;2. School of Mathematics and Statistics, Beijing Key Laboratory on MCAACI, Beijing Institute of Technology, Beijing 100081, PR China |