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2. A. R. C. Westwood andN. H. Macmillan, ?Science of Hardness Testing? (ASM, Cleveland, Ohio 1973) p. 377.
3. N. H. Macmillan, R. D. Huntington andA. R. C. Westwood,Phil. Mag. 28 (1973) 923.
4. A. R. C. Westwood, N. H. Macmillan andR. S. Kalyoncu,J. Amer. Ceram. Soc. 56 (1973) 258.
5. Idem, Trans. AIME (Mining), in press.