1. 1. Suzuki, S., Tsuneya, Y, and Baba, M. (1984) : Clin. Virol., 12, 150-153 (text in Japanese) .
2. 2. Moritsugu, Y., Tanaka, T, and Shikata, T. (1978) : Japan. J. Med. Sci. Biol., 31, 325-338.
3. 3. Pohjanpelto, P, and Lahdensivu, R. (1984) : Scand. J. Infect. Dis., 16, 229-233.
4. 4. Hsu, H. Y., Chang, M. H., Chen, D. S., Lee, C. Y, and Sung, J. L. (1985) : J. Med. Virol., 17, 297-301.
5. 5. Committee on Epidemic Diseases, Ministry of Health, Singapore 0922 (1986) : Enidemiol. News Bull., XII, 51-54.