Danagulyan, G. G.; Balasanyan, N. G.; Terent'ev, P. B.; Zalinyan, M. G. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1989 , vol. 25, # 12 p. 1369 - 1373 Khimiya Geterotsiklicheskikh Soedinenii, 1989 , # 12 p. 1644 - 1648