1. 1. McDonald, A. D., Williams, M. C., West, R, and Stewart, J. (1974) : Amer. J. Epidemiol., 100, 124-129.
2. 2. Hondo, R. (1974) : Japan. J. Med. Sci. Biol., 27, 205-213.
3. 3. Nagafuchi, S., Oda, H., Mori, R, and Taniguchi, T. (1979) : J. Gen. Virol., 44, 715-723.
4. 4. Tateno, I., Yokoyama, T., Suzuki, S., Sugiura, A, and Fukaya, I. (1958) : Japan. J. Exptl. Med., 28, 375-380.
5. 5. Yamaguchi, S. (1959) : Nihon Eiseigaku Zasshi, 13, 848-853 (in Japanese) .