Portnov, Yu. N.; Zabrodnyaya, V. G.; Voronin, V. G.; Kost, A. N.
Chemistry of Heterocyclic Compounds (New York, NY, United States), 1982 , vol. 18, # 7 p. 703 - 706
Khimiya Geterotsiklicheskikh Soedinenii, 1982 , # 7 p. 926 - 929