1. N. A. Milas and W. L. Walsh, J. Am. Chem. Soc., 57, 1389 (1935).
2. E. Lukevics (editor), Advances in the Chemistry of Furan [in Russian], Zinatne, Riga (1978), p. 100.
3. M. V. Shimanskaya, S. A. Hiller, and I. I. Ioffe, Vapor-Phase Contact Oxidation of Furan Compounds [in Russian], Zinatne, Riga (1971).
4. S. A. Hiller and M. V. Shimanskaya, The Mechanism of Catalytic Oxidation Reactions of Furan and Pyridine Compounds [in Russian], Nauka, Moscow (1973), p. 47.
5. M. V. Shimanskaya, Contact Reactions of Furan Compounds [in Russian], Zinatne, Riga (1985).