Mitskyavichyus, V. Yu.; Baltrushis, R. S. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1992 , vol. 28, # 10 p. 1185 - 1188 Khimiya Geterotsiklicheskikh Soedinenii, 1992 , # 10 p. 1391 - 1394