Yun, L. M.; Yangibaev, S.; Shakhidoyatov, Kh. M.; Alekseeva, V. Ya.; V'yunov, K. A. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1986 , vol. 22, # 9 p. 1001 - 1003 Khimiya Geterotsiklicheskikh Soedinenii, 1986 , vol. 22, # 9 p. 1236 - 1238