Orlov, V. D.; Vorob'eva, N. P.; Tishchenko, A. A.; Pikalev, O. M.; Popov, V. I.; Yagupol'skii, L. M.
Chemistry of Heterocyclic Compounds (New York, NY, United States), 1991 , vol. 27, # 9 p. 942 - 946
Khimiya Geterotsiklicheskikh Soedinenii, 1991 , # 9 p. 1179 - 1184