1. Science Division, College of Education, University of The Ryukyus, Nishihara, Okinawa 903-01
2. Department of Pure and Applied Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153
3. Physics Division, Faculty of Education, Kobe University, 3-11 Tsurukabuto, Nada-ku, Kobe 657