1. Theoretical Physics, Gesellschaft für Schwerionenforschung GSI P.O. Box 110552, D-64220 Darmstadt, Germany
2. Division of Natural Science, Meiji University, Izumi Campus Eifuku, Suginami-ku, Tokyo 168, Japan
3. Waseda University High School 3–31–1 Kanishakuji, Nerima-ku, Tokyo 177, Japan