El'chaninov, M. M.; Simonov, A. M.; Oleinikova, L. Ya. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1983 , p. 1041 - 1043 Khimiya Geterotsiklicheskikh Soedinenii, 1983 , vol. 19, # 10 p. 1311 - 1313