1. AIZAWA, K. and M. OHBA (1978) Proc. Seric. Sci. Kyushu, No. 9: p. 48 (in Japanese).
2. BELLETT, A. J. D. and E. H. MERCER (1964) Virology 24: 645-653.
3. CERUTTI, M. and G. DEVAUCHELLE (1979) Arch. Virol. 61 : 149-155.
4. GRACE, T. D. C. (1962) Nature 195: 788-789.
5. OHBA, M. (1975) Sci. Bull. Fac. Agric. Kyushu Univ. 30: 51-65 (in Japanese with an English sum-mary).