1. R. Neidlein and E. Berhard, Arch. Pharm., 311. 714 (1978).
2. Aki Osami and Nakagawa Vasushi, Chem. Pharm. Bull., 20, 1325 (1972).
3. S. Seshadri, J. Sci. Ind. Res., 32, 128 (1973).
4. M. R. Chandromohan and S. Seshadri, Indian J. Chem., 12, 940 (1974).
5. Z. F. Solomko, V. I. Sheremet, M. P. Khmel', V. I. Avramenko, and V. N. Proshkina, Khim. Geterotsikl. Soedin., No. 3, 405 (1982).