1. Piggott, M. R., and Wilman, H., Paper 18, Conference on Lubrication and Wear, Inst. Mech. Eng., London, (October 1957).
2. Spurr, R. T., and Newcomb, T. P., Paper 28, Conference on Lubrication and Wear, Inst. Mech. Eng., London, (October 1957).
3. Bowden, F. P., and Tabor, D., “The Friction and Lubrication of Solids”, 2nd edn. (Clarendon Press, Oxford, 1954).
4. Khruschov, M. M., Paper 46, Conference on Lubrication and Wear. Inst. Mech. Eng., London, (October 1957).