1. A. Kelly, ?Strong Solids? (Clarendon, Oxford, 1966).
2. D. Tabor, ?Hardness of Metals? (Clarendon, Oxford, 1951).
3. M. T. Huber, Ann. Physik 14 (1904) 153.
4. M. V. Swain, Ph.D. Thesis, University of New South Wales, 1973.
5. B. R. Lawn and T. R. Wilshaw, ?Fracture of Brittle Solids? (Cambridge University Press, Cambridge, in press), Ch. 3.