Gol'dfarb, Ya. L.; Kalik, M. A.; Kozlova, Z. G. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1980 , p. 1007 - 1011 Khimiya Geterotsiklicheskikh Soedinenii, 1980 , vol. 16, # 10 p. 1331 - 1336