1. See, for example,D. Mclean, ?Grain Boundaries in Metals? (Clarendon Press, Oxford, 1957) p. 239.
2. C. S. Smith,Trans. Amer. Inst. Min. Metall. Engrs. 175 (1948) 15.
3. G. D. Miles, R. A. J. Sambell, J. Rutherford, andG. W. Stephenson,Trans. Brit. Ceram. Soc. 66 (1967) 319.
4. C. S. Smith,Met. Rev. 9 (1964) 1.
5. N. A. Haroun, Ph.D. thesis, University of Sheffield (1967).