Institute of Mathematics University of Debrecen Number Theory Research Group Hungarian Academy of Sciences and University of Debrecen P.O. Box 12 H–4010 Debrecen HUNGARY
János Folláth
Faculty of Informatics University of Debrecen P.O. Box 12 H–4010 Debrecen HUNGARY
Attila Pethő
Faculty of Informatics University of Debrecen P.O. Box 12 H–4010 Debrecen HUNGARY