1. M. C. Naik, J. M. Dupouy and Y. Adda, Mémoires Scientifiques Rev. Metallurg. 63, 88 (1966).
2. J. M. Bupouy, J. Mathie and Y. Adda, Mémoires Scientifiques Rev. Metallurg. 63, 481 (1966).
3. A. D. LeClaire, Phil. Mag. 7, 141(1962).
4. Examples of such discrepancies are given in Ref. 5.
5. G. M. Hood, Phil. Mag. 21, 305 (1970).