1. R.S. Hayano, Y.J. Uemura, J. Imazato, N. Nishida, K. Nagamine, T. Yamazaki and H. Yasuoka, Phys. Rev. Lett. 41 (1978) 421
2. Y.J. Uemura, N. Nishida, J. Imazato, R.S. Hayano, M. Takigawa and T. Yamazaki, this conference
3. R.S. Hayano, Y.J. Uemura, J. Imazato, N. Nishida, T. Yamazaki, H. Yasuoka and Y. Ishikawa, Phys. Rev. Lett. 41 (1978) 1743
4. M. Takigawa, H. Yasuoka, Y.J. Uemura, R.S. Hayano, T. Yamazaki and Y. Ishikawa, this conference
5. N. Nishida, K. Nagamine, R.S. Hayano, Y.J. Uemura, J. Imazato, T. Yamazaki, H. Miyajima, W.S. Chan and S. Chikazumi, Proc. 5th Int. Conf. Positron Annhilation (Japan, 1979), p. 74