Terent'ev, P. B.; Ch'in, Lieh T'i; Kost, A. N. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1981 , vol. 17, # 6 p. 591 - 593 Khimiya Geterotsiklicheskikh Soedinenii, 1981 , # 6 p. 800 - 802