1. A. Kelly, ?Strong solids? (Clarendon Press, Oxford 1986) p. 157.
2. D. K. Hale,J. Mater. Sci. 11 (1976) 2105.
3. H. A. Goldberg, US patent 4725940 (Hoechst Celanese Corporation).
4. A. K. Bhattacharya, A. Hartridge, K. K. Mallick andD. M. Taylor,J. Mater. Sci. (1996).
5. T. Furuya, UK patent application G13 2028788, March 1980.