∗Martin GAVALEC, ∗∗Ján PLAVKA ∗Department of Information Technologies, Faculty of Informatics and Management, University of Hradec Králové, Rokitanského 62, 500 03 Hradec Králové, Czech Republic E-mail: [email protected] ∗∗Department of Mathematics, Faculty of Electrical Engineering and Informatics, Technical University of Košice, B. Němcovej 32, 042 00 Košice, tel. 095/602 3256, E-mail: J...
