Yurovskaya, M. A.; Afanas'ev, A. Z.; Chertkov, V. A.; Gizatullina, E. M.; Bundel', Yu. G. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1987 , vol. 23, # 12 p. 1305 - 1308 Khimiya Geterotsiklicheskikh Soedinenii, 1987 , # 12 p. 1625 - 1628