Semeikin, A.S.; Koifman, O.I.; Berezin, B.D. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1986 , vol. 22, # 4 p. 397 - 401 Khimiya Geterotsiklicheskikh Soedinenii, 1986 , vol. 22, # 4 p. 486 - 490