1. Belinskey, V. A., and Zakharav, V. E. (1978).Zhurnal Eksperimental'noi i Teoreticheskoi Fiziki,75, 1953.
2. Belinskey, V. A., and Zakharav, V. E. (1979).Zhurnal Eksperimental'noi i Teoreticheskoi Fiziki,77, 3.
3. Gao, Y. J., and Zhong, Z. Z. (1992).Journal of Mathematical Physics,33, 278.
4. Letelier, P. S. (1984).Journal of Mathematical Physics,25, 2675.
5. Letelier, P. S. (1985).Journal of Mathematical Physics,26, 467.