Cherkasov, V. M.; Remennikov, G. Ya.; Kisilenko, A. A. Chemistry of Heterocyclic Compounds (New York, NY, United States), 1982 , p. 526 - 529 Khimiya Geterotsiklicheskikh Soedinenii, 1982 , vol. 18, # 5 p. 691 - 694