1. Laboratory
of Molecular Structure and Dynamics, Institute of Chemistry, Eötvös Loránd University, P.O. Box 32, H-1518 Budapest 112, Hungary
2. MTA-ELTE Complex Chemical Systems Research Group, Pázmány Péter sétány 1/A, H-1117 Budapest, Hungary
3. Department
of Algebra and Number Theory, Institute of Mathematics, Eötvös Loránd University, P.O. Box 120, H-1518 Budapest 112, Hungary