Tikhomirov, D. A.; Porchinskaya, N. M.; Eremeev, A. V. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1989 , vol. 25, # 5 p. 498 - 501 Khimiya Geterotsiklicheskikh Soedinenii, 1989 , # 5 p. 600 - 603