Portnov, Yu. N.; Zabrodnyaya, V. G.; Voronin, V. G.; Kost, A. N.
Chemistry of Heterocyclic Compounds (New York, NY, United States), 1983 , vol. 19, # 11 p. 1175 - 1179
Khimiya Geterotsiklicheskikh Soedinenii, 1983 , # 11 p. 1485 - 1489