1. Kossuth University, Institute of Experimental Physics, H-4001 Debrecen, Pf. 105, Hungary
2. Bulgarian Academy of Sciences, Institute for Nuclear Research and Nuclear Energy Tzarigradsko chausse 72, 1784 Sofia, Bulgaria
3. Institute of Nuclear Research of the Hungarian Academy of Sciences P.O.B. 51, H-4001 Debrecen, Hungary
4. Kitahassaku 60, Midori-ku, Yokohama, Knagawa-ken 226, Japan