1. V. G. Drinfel'd, Zap. Nauchn. Sem. LOMI,155, 18?49 (1986).
2. V. G. Drinfel'd, Dokl. Akad. Nauk SSSR,283, No. 5, 1060?1064 (1985).
3. P. P. Kulish and E. K. Sklyanin, Zap. Nauchn. Sem. LOMI,95, 129?160 (1980).
4. M. L. Nazarov, Lett. Math. Phys.,21, 123?131 (1991).
5. V. G. Kac, Adv. Math.,26, 8?96 (1977).