Kremzer, A. A.; Strokin, Yu. V.; Klyuev, N. A.; Buryak, V. P.
Chemistry of Heterocyclic Compounds (New York, NY, United States), 1981 , vol. 17, # 8 p. 821 - 824
Khimiya Geterotsiklicheskikh Soedinenii, 1981 , # 8 p. 1102 - 1105