1. M. D. Mashkovskii, Drugs, Part 1 [in Russian], 8th Edition, Moscow (1977), pp. 484–487.
2. British Patent No. 919073.
3. South African Patent No. 6704340.
4. West German Patent No. 1238920.
5. M. C. Fioretti and A. Martani, Ann. Fac. Med. Perugia,59, 703 (1968).