Yusubov, M. S.; Krasnokutskaya, E. A.; Filimovov, V. D.; Kovaleva, L. F. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1992 , vol. 28, # 11 p. 1260 - 1263 Khimiya Geterotsiklicheskikh Soedinenii, 1992 , # 11 p. 1477 - 1480