1. Insitute of Nuclear Research of the Hungarian Academy of Sciences, Debrecen, Pf. 51, Hungary-4001, Hungary
2. Insitute of Experimental Physiscs, University of Debrecen, Debrecen, Pf. 105 Hungary-4010, Hungary
3. Universidad Autonoma de la Ciudad de Mexico, Prolongacion San Isidro 151, Col. San Lorenzo Tezonco, Del Iztapalapa, Mexico City, 09790 D. F., Mexico
4. Institute de Ciencias Nucleares, Universidad National Autonoma de Mexico, A. P. 70-543, Mexico City, 04510 D. F., Mexico