Vinograd, L. Kh.; Suvorov, N. N. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1984 , vol. 20, # 9 p. 984 - 988 Khimiya Geterotsiklicheskikh Soedinenii, 1984 , vol. 20, # 9 p. 1206 - 1210