1. V. I. Dulenko, V. I. Volbushko, L. V. Dulenko, and G. N. Dorofeenko, Khim. Geterotsikl. Soedin., No. 2, 273 (1974).
2. S. V. Krivun, V. I. Dulenko, L. V. Dulenko, and G. N. Dorofeenko, Dok1. Akad. Nauk SSSR, 166, 359 (1966).
3. F. D'Alo, A. Masserini, and F. Bonacina, Boll. Chim. Farm., 103, 709 (1964).
4. F. Sauter and A. Barakat, Montash. Chem., 98, 2393 (1967).
5. F. Sauter and F. Ecker, Monatsh. Chem., 99, 610 (1968).