Gevaza, Yu. I.; Kupchik, I. P.; Staninets, V. I. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1981 , vol. 17, # 1 p. 24 - 26 Khimiya Geterotsiklicheskikh Soedinenii, 1981 , # 1 p. 32 - 34