Kotovskaya, S. K.; Mokrushina, G. A.; Postovskii, I. Ya.; Polyakova, M. V. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1981 , vol. 17, # 5 p. 480 - 483 Khimiya Geterotsiklicheskikh Soedinenii, 1981 , # 5 p. 654 - 657