Murza, M.M.; Tarasenko, A. E.; Safarov, M. G. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1991 , vol. 27, # 7 p. 708 - 710 Khimiya Geterotsiklicheskikh Soedinenii, 1991 , # 7 p. 897 - 899