1. A Chatteijee, S Pakrashi, and G Werner, in: Fortschritte der Chemie Organischer Naturstoffe; Vol. 13, L Zechmeister, Ed., Springer-Verlag, Vienna, 1956, pp. 346–443.
2. RE Woodson, HW Younken, E Schüttler, and TA Schneider, Rauwolfia: Botany, Pharmacognosy, Chemistry and Pharmacology, Little Brown and Co., Boston, 1957.
3. L Toke and C Szantay, Heterocycles 4:251 (1976).
4. JP Kutney, in: The Total Synthesis of Natural Products; Vol. 3, J ApSimon, Ed., John Wiley and Sons, New York, 1977, pp. 273–438.
5. DR Dalton, The Alkaloids: The Fundamental Chemistry-A Biogenetic Approach, Marcel Dekker, Inc., New York, 1979, pp. 415–628.