Daukshas, V. K.; Martinkus, R. S.; Gineitite, V. L.; Urbonene, S. L. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1982 , vol. 18, # 9 p. 932 - 937 Khimiya Geterotsiklicheskikh Soedinenii, 1982 , # 9 p. 1215 - 1219