Gol'dfarb, Ya. L.; Gromova, G. P.; Belen'kii, L. I. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1986 , vol. 22, # 6 p. 663 - 666 Khimiya Geterotsiklicheskikh Soedinenii, 1986 , vol. 22, # 6 p. 837 - 840