1. V. M. Salo, Med. Prom., No. 4, 43–47 (1960).
2. V. M. Salo, Aptechnoe Delo,12, 40–43 (1963).
3. P. Gasic and M. Popovic, Planta Med.,36, No. 3, 260–261 (1979).
4. M. K. Yusupov and A. S. Sadykov, Khim. Prir. Soedin., No. 1, 3–26 (1978).
5. A. Brossi, The Alkaloids: Chemistry and Pharmacology, Vol. XXIII, Academic Press, New York (1984).