Drevko, B. I.; Fomenko, L. Al; Kharchenko, V. G. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1989 , vol. 25, # 6 p. 632 - 634 Khimiya Geterotsiklicheskikh Soedinenii, 1989 , vol. 25, # 6 p. 767 - 769