Gribkov, A.A.; Borovkov, V.V.; Evstigneeva, R.P.; Sakata, Y. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1994 , vol. 30, # 8 p. 905 - 915 Khimiya Geterotsiklicheskikh Soedinenii, 1993 , # 8 p. 1052 - 1062