1. Department of Theoretical Physics, University of Debrecen, H-4010 Debrecen, PO Box 5, Hungary
2. Department of Information Technology, University of Debrecen, H-4010 Debrecen, PO Box 12, Hungary
3. Institut de Chimie, Laboratoire de Chimie Quantique, UMR 7177, CNRS/Université de Strasbourg, 4 rue Blaise Pascal, 67000 Strasbourg, France
4. Theoretische Chemie, Physikalisch-Chemisches Institut, Universität Heidelberg, Heidelberg D-69120, Germany