1. Department of Mathematics, Faculty of Basic Science, Babol Noshirvani University of Technology, Shariati Ave., Babol, 47148-71167, Iran
2. Department of Mathematics and Descriptive Geometry, Faculty of Civil Engineering, Slovak University of Technology, SK-810 05 Bratislava, Slovakia
3. Institute of Information Theory and Automation of the Czech Academy of Sciences, Pod vodàrenskou věži 4, 182 08 Praha 8, Czech Republic