Ivanov, E. I.; Polishchuk, A. A.; Mazepa, A. V. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1992 , vol. 28, # 9 p. 1006 - 1008 Khimiya Geterotsiklicheskikh Soedinenii, 1992 , # 9 p. 1193 - 1195