Gitis, K. M.; Neumoeva, G. E.; Isagulyants, G. V. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1993 , vol. 29, # 11 p. 1308 - 1315 Khimiya Geterotsiklicheskikh Soedinenii, 1993 , # 11 p. 1516 - 1525