1. B. Cockayne, M. Chesswas, andD. B. Gasson,J. Matls. Sci. 2 (1967) 7.
2. W. Bardsley andB. Cockayne, ?Crystal Growth?, Proceedings of International Conference on Crystal Growth, Boston, 1966 (Pergamon Press, 1967), p. 109.
3. M. Chesswas andB. Cockayne, unpublished work.