Vereshchagin, L. I.; Maksikova, A. V.; Tikhonova, L. G.; Buzilova, S. R.; Sakovich, G. V. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1981 , vol. 17, # 5 p. 510 - 515 Khimiya Geterotsiklicheskikh Soedinenii, 1981 , # 5 p. 688 - 693