1. Department of Information
Technology, University of Debrecen, H-4010 Debrecen, P.O. Box 12, Hungary
2. Theoretische
Chemie, Physikalish-Chemisches
Institut, Universität Heidelberg, H-69120 Heidelberg, Germany
3. Department of Theoretical
Physics, University of Debrecen, H-4010 Debrecen, P.O. Box 5, Hungary