Institution: | 1. Institute of Mathematics, University of Rzeszów , Rejtana 16A, 35-959 , Rzeszów , Poland aniam@univ.rzeszow.pl;3. Institute of Computer Science, Jagiellonian University , ?ojasiewicza 6, 30-348 , Kraków , Poland;4. Institute of Mathematics, University of Rzeszów , Rejtana 16A, 35-959 , Rzeszów , Poland |