1. Catalyst Handbook;Bridger,1970
2. 2. A. L. Hausberger, C. B. Knight, and K. Attwood in L. Seglin (Ed.), Methanation of Synthesis Gas, Advances in Chemistry Series No. 146, A. C. S., Washington, (1975), p47.
3. 4. L. A. Heathcote, W. G. Bugden and A. S. Pratt, U. K. Patent 1,492,929.