1. R. F. Bunshah andR. W. Armstrong, in ?The Science of Hardness Testing and its Research Applications?, edited by J. H. Westbrook and H. Conrad (ASM, Metals Park, 1973) Chapter 26.
2. R. W. Armstrong andW. H. Robinson,N.Z.J. Sci. 17 (1974) 429.
3. Idem submitted toJ. Mech. Phys. Solids.
4. W. J. Cousins, R. W. Armstrong andW. H. Robinson,J. Mater Sci. 10 (1975) 1655.
5. H. R. Hertz, ?Miscellaneous Papers? (Macmillan, London 1896) Chapters 5 and 6.