1. D. Petrasek and J. Weeton, Trans. TMS-AIME 230 (1964) 977.
2. D. Cratchley, Powder Met. 11 (1963) 59.
3. J. A. Alexander, Quarterly Progress Report No. 6, Contract AF 33 (615)-2862, January 1967, General Technologies Corporation.
4. D. Cratchley, Met. Rev. 10 (1965) 85.
5. See for example, C. Herring, ?Structure and Properties of Solid Surfaces?, ed. R. Gomer and C. S. Smith (The University of Chicago Press, Chicago, 1953).