1. R. Jettrand, 3rd Congress European Federation of Chem. Eng., London, 1962.
2. British Patent 1,194,181, 1967.
3. D.S. Flett:Chem. and Ind., 1972, vol. 52, pp. 983–88.
4. B.J. Sabacky and J. W. Evans:Metall. Trans. B, 1977, vol. 8B, pp. 5–13.
5. F. Goodridge, D. I. Holden, H. P. Murray, and R. F. Plimley:Trans. Inst. Chem. Eng., 1971, vol. 49, pp. 128–36.