Bredikhina, Z. A.; Buzykin, B. I.; Kitaev, Yu. P. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1991 , vol. 27, # 4 p. 427 - 433 Khimiya Geterotsiklicheskikh Soedinenii, 1991 , # 4 p. 537 - 543