1. Bostock, W., J. Sci. Inst., 29, 209 (1952).
2. Harris, C. C., J. App. Phys., 31, 215 (1960).
3. Heywood, H., Recent Developments in Mineral Dressing, 31 (I.M.M. London, 1953).
4. Frangiskos, N. Z., Harris, C. C., and Jowett, A., Third Intern. Cong. Surface Activity, Paper D46 (Cologne, 1960).