Kost, A. N.; Terenin, V. I.; Yudin, L. G.; Sagitullin, R. S. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1980 , p. 965 - 969 Khimiya Geterotsiklicheskikh Soedinenii, 1980 , vol. 16, # 9 p. 1272 - 1277