Affiliation: | a Max-Planck-Institut für Physik und Astrophysik, Werner-Heisenberg-Institut für Physik, P.O. Box 401212, W-8000, Munich, FRG b L.D. Landau Institute for Theoretical Physics, SU-142 432, Chernogolovka (Moscow Region, USSR Research Institute for Nuclear Physics, Moscow State University, SU-117 234, Miscow, USSR |