1. V. G. Drinfeld, Dokl. Acad. Nauk SSSR, 273 (1983).
2. A. N. Kirillov and N. Yu. Reshetikhin, Comm. Math. Phys., 134, 421–431 (1990).
3. P. Etingof, O. Schiffman, and T. Schedler, JAMS, 134, 595–609 (2000).
4. A. Alekseev and A. Lachowska, “Invariant *-product on coadjoint orbits and the Shapovalov pairity,” math. QA/0308100.
5. A. Elashvili, Funct. Anal. Prilozhen., 16, 94–95 (1982).