1. H. O’Neill’s, The Hardness of Metals and Its Measurement (Chapman and Hall, London, 1934).
2. F.C. Lea, Hardness of Metals (Griffin, London, 1936).
3. S.R. Williams, Hardness and Hardness Measurements, Amer. Soc. Met. 1942.
4. D. Tabor, The Hardness of Metals (Clarendon Press, Oxford, 1951).
5. A.G. Atkins, A. Silverio, and D. Tabor, J. Inst. Met. 94, 369 (1966).