1. G. B. Elikov and V. A. Stonik,The Steroids of Marine Organisms [in Russian], Nauka, Moscow (1988).
2. N. V. Kovganko and A. A. Akhrem,Steroids: Ecological Functions [in Russian], Nauka i Tekhnika, Minsk (1990).
3. D. M. Piatak and J. Wicha,Chem. Rev.,78, No. 3, 199 (1978).
4. J. Redpath and F. J. Zeelen,Chem. Soc. Rev.,12, No. 1 75 (1983).
5. V. N. Zhabinskii, V. K. Ol'khovik, and V. A. Khripach,Zh. Org. Khim.,32, No. 3, 327 (1996).