Ibatullin, U. G.; Pavlov, Yu. V.; Safarov, M. G. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1990 , vol. 26, # 2 p. 155 - 157 Khimiya Geterotsiklicheskikh Soedinenii, 1990 , vol. 26, # 2 p. 183 - 186