Krauze, A. A.; Kalme, Z. A.; Pelcher, Yu. E.; Liepin'sh, E. E.; Dipan, I. V.; Dubur, G. Ya.
Chemistry of Heterocyclic Compounds (New York, NY, United States), 1983 , vol. 19, # 11 p. 1202 - 1207
Khimiya Geterotsiklicheskikh Soedinenii, 1983 , # 11 p. 1515 - 1520