Chupakhin, O. N.; Baklykov, V. G.; Klyuev, N. A.; Matern, A. I. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1989 , vol. 25, # 8 p. 904 - 907 Khimiya Geterotsiklicheskikh Soedinenii, 1989 , # 8 p. 1083 - 1087