Orlova, T. I.; Epshtein, S. P.; Tashchi, V. P.; Putsykin, Yu. G. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1991 , vol. 27, # 4 p. 433 - 437 Khimiya Geterotsiklicheskikh Soedinenii, 1991 , # 4 p. 544 - 548