1. Computer Science, Laurentian University, Sudbury, Ontario P3E 2C6, Canada. wkoczkodaj@cs.laurentian.ca
2. Institute of Mathematics and Cryptology, Faculty of Cybernetics, Military University of Technology, ul. Kaliskiego 2, 00-908 Warsaw, Poland. ryszard.smarzewski@gmail.com
3. AGH University of Science and Technology, Faculty of Applied Mathematics, al. Mickiewicza 30, 30-059 Krakow, Poland. szybowsk@agh.edu.pl