Fisyuk, A. S.; Ryzhova, E. V.; Unkovskii, B. V. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1994 , vol. 30, # 2 p. 238 - 242 Khimiya Geterotsiklicheskikh Soedinenii, 1994 , # 2 p. 260 - 265