1. Institute of Theoretical and Applied Informatics, Polish Academy of Sciences, ul. Bałtycka 5, 44-100 Gliwice, Poland
2. Institute of Informatics, Silesian University of Technology, ul. Akademicka 16, 44-100 Gliwice, Poland
3. Institute of Mathematics, Silesian University of Technology, Kaszubska 23, 44-100 Gliwice, Poland