1. T. A. Davies, Proc. IEE Symposium on Switching Techniques for Telecommunication Networks, 21?25 April 1969, No. 52, p. 24?27.
2. B. P. Richards,Metal Finishing Journal, Aug./Sept. (1971) 208.
3. Idem, Hirst Research Centre, GEC Ltd, Wembley, private communication.
4. M. V. Speight,J. Nucl. Mat. 12 (1964) 1216.
5. R. D. Daniels,J. Appl. Phys. 42 (1971) 417.