1. D. C. SMITH. Brit. Dent. J. 125 (1968) 381.
2. D. F. WILLIAMS and J. CUNNINGHAM. ?Materials in clinical dentistry? (Oxford University Press, Oxford, 1979).
3. A. D. WILSON. Chem. Soc. Rev. 7 (1978) 254.
4. N. N. GREENWOOD and A. EARNSHAW, ?The chemistry of the elements? (Pergamon Press, Oxford, 1984).
5. A. D. WILSON, J. Biomed. Mater. Res. 16 (1982) 549.