1. N. M. Omar, Indian J. Chem., No. 17, 27 (1974).
2. K. Hideg, O. Hideg, F. Varga, and E. Fischer, West German Patent No. 1933666; Chem. Abstr., 73, 99002 (1970).
3. W. Werner, W. Zschiesche, J. Guetther, and H. Heinecke, Pharmazie, 31, 282 (1976).
4. V. D. Orlov, N. N. Kolos, F. G. Yaremenko, and V. F. Lavrushin, Khim. Geterotsikl. Soedin., No. 5, 697 (1980).
5. Sadtler Research Laboratories, Catalog of Spectra, Philadelphia, USA (1972), ref. 4063.