1. P. Ward and G. M. Ballard, US Patent 4 205 976 (1980).
2. R. Gardon, in ?Glass Science and Technology?, Vol. 5, edited by D. R. Uhlmann and N. J. Kreidl (Academic, New York, 1980) pp. 145?216.
3. S. S. Kistler, J. Amer. Ceram. Soc. 45(2) (1962) 59.
4. R. F. Bartholomew and H. M. Garfinkel, in ?Glass Science and Technology?, Vol. 5, edited by D. R. Uhlmann and N. J. Kreidl (Academic, New York, 1980) pp. 217?70.
5. AWRE Report;I. W. Donald,1984