1. N. L. Parr andE. R. W. May,Proc. Brit. Ceram. Soc. 7 (1967) 81.
2. D. J. Goodfrey,Metals and Materials 2 (1968) 305.
3. A. F. McLean,Bull. Amer. Ceram. Soc. 52 (1973) 464, 482.
4. R. F. Coe, R. J. Lumby andM. F. Pawson, “Special Ceramics 5”, edited by P. Popper (British Ceramic Research Association, Stoke-on-Trent, 1972) p. 361.
5. W. C. Riley andJ. H. Richardson, “Modern Ceramics”, edited by J. E. Hove and W. C. Riley (Wiley, New York, 1965) p. 177.