1. E. Schmidt, West German Pat. No. 2,060,614; Ref. Zh. Khim., 2N231P (1981).
2. M. Hayami and S. Torikoshi, US Pat. No. 4,314,058; Ref. Zh. Khim., 2N254P (1983).
3. Yu. A. Degutis, A. A. Shachkus, and A. G. Urbonavichyus, Khim. Geterotsikl. Soedin., No. 7, 933 (1985).
4. A. A. Shachkus and R. Yu. Degutite, Khim. Geterotsikl. Soedin., No. 8, 1056 (1986).
5. M. Wakselman, G. Decodts, and M. Vikas, Compt. rend., C, No. 267, 1063 (1968).