Savel'ev, V. L.; Samsonova, O. L.; Troitskaya, V. S.; Vinokurov, V. G.; Lezina, V. P.; Smirnov, L. D. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1988 , p. 805 - 810 Khimiya Geterotsiklicheskikh Soedinenii, 1988 , vol. 24, # 7 p. 977 - 981