Morkovnik, A. S.; Okhlobystin, O. Yu. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1985 , vol. 21, # 4 p. 461 - 464 Khimiya Geterotsiklicheskikh Soedinenii, 1985 , vol. 21, # 4 p. 551 - 554