Belen'kii, L.I.; Antonov, D.M.; Dudinov, A.A.; Lubuzh, E.D.; Krayushkin, M.M. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1993 , vol. 29, # 1 p. 109 - 114 Khimiya Geterotsiklicheskikh Soedinenii, 1993 , # 1 p. 124 - 129