1. H.I. Merriam, U.S. Pat. 1,737,320 (1929).
2. T.V. Fowler, U.S. Pat. 1,930,125 (1933).
3. N.A. Laury, U.S. Pat. 2,142,855 (1939).
4. The Chemistry of Catalytic Hydrocarbon Conversions;Pines,1981
5. Oxidations carried out by means of vanadium oxide catalysts