1. Department of Electrical Engineering and Computer Science, University of Kansas Lawrence, KS 66045, USA and Institute of Computer Science, Polish Academy of Sciences, 01–237 Warsaw, Poland. E-mail: jerzy@eecs.ukans.edu
2. Department of Computer Science, University of Rzeszow, 35–310 Rzeszow, Poland. E-mail: wrzasa@univ.rzeszow.pl