1. Mills, G. A. Chem. Technol. 418 (1972); Am. chem. Soc. Division of Fuel Chemistry preprint (1972).
2. Kirk, E. R. & Othmer, D. F. Encyclopedia of Chemical Technology, Vol. 4 (Interscience, New York, 1966).
3. Squires, A. M. Science 184, 340–46 (1974).
4. Clingman, G. E. & Schaaf, R. P. Hydrocarbon Processing 97–101 (1972).
5. Verma, A. Chem. Technol. 372–81 (1978).