1. M. D. Mashkovskii, Drugs [in Russian], Moscow, Part I (1977), p. 123.
2. State Pharmacopeia of the USSR, 10th Edn. [in Russian], Moscow (1968).
3. G. A. Melent'eva, Pharmaceutical Chemistry [in Russian], Moscow, Vol. 2 (1976), p. 492.
4. P. L. Senov, A Course of Pharmaceutical Chemistry [in Russian], Moscow (1952), p. 443.
5. A. P. Orekhov, The Chemistry of the Alkaloids [in Russian], Moscow (1953).