1. G.A. Michelson, U.S. Patents 3.749,663, 3,749,664, 3,755,148, 3,755,150, 3,755,196 (1973).
2. C.W. Fitz and H.F. Rase, Ind. Eng. Chem. Prod. Res. Dev., 22(1983)44.
3. J.D Colgan and Y. Chonitz, U.S. Patent 3,287,280(1966).
4. J.N. Haresnape and J.E. Morris, UK patent 701,217(1953).
5. D. Chadwick and D.W. Aitchison, in “Preparation of Catalysts III”, es. Poncelet, Grange and Jacobs, (Elseviers, Amsterdam, 1982) p. 323.