Salekh, M.A.; Kurkovskaya, L.N.; Krasavina, L.S.; Persianova,I.V.; Vigdorchik, M.M.; Suvorov, N.N. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1988 , p. 624 - 627 Khimiya Geterotsiklicheskikh Soedinenii, 1988 , vol. 24, # 6 p. 766 - 769