1. A. H. Cottrell, Proc. Roy. Soc. A 282 (1964) 2.
2. A. Kelly, ibid 63.
3. H. G. Tattersall, and G. Tappin, J. Mater. Sci. 1 (1966) 296.
4. A. Kelly, and W. R. Tyson, Proc. 2nd International Materials Symposium, California, 1964 (J. Wiley, New York and London).
5. A. Kelly and G. J. Davies, Met. Revs. 10 (1965) 37.