Dankova, E. F.; Bakulev V. A.; Kolobov M. Yu.; Andosova G. V.; Mokrushin, V. S. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1989 , vol. 25, # 6 p. 688 - 690 Khimiya Geterotsiklicheskikh Soedinenii, 1989 , # 6 p. 827 - 829