1. V. V. Zatula, N. P. Maksyutina, and D. G. Kolesnikov, KhPS [Chemistry of Natural Compounds],1, 153, 1965.
2. V. V. Zatula, N. V. Chernobrovaya, and D. G. Kolesnikov, KhPS [Chemistry of Natural Compounds],2, 438, 1966.
3. L. Fieser and M. Fieser, Steroids [Russian translation], Moscow, p. 188, 1964.
4. A. Katz, Helv. Chim., Acta,40, 831, 1957.
5. L. F. Fieser and T. Goto, J. Am. Chem. Soc.,82, 1697, 1960.