Bespalov, B. P.; Getmanova, E. V. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1981 , vol. 17, # 3 p. 225 - 228 Khimiya Geterotsiklicheskikh Soedinenii, 1981 , vol. 17, # 3 p. 317 - 320