1. G. J. Copley, A. D. Rivers and R. Smith, Glass Tech. 13 (2) (1972) 50.
2. Idem, J. Mater. Sci. 8 (1973) 1049.
3. J. C. Chaston, Plat. Met. Rev. 9 (4) (1965) 126.
4. R. Katzschmann, Silik Tech. 18 (7) (1967) 211.
5. J. A. Pask, ?Modern Aspects of the Vitreous State?, Vol. 3 (Butterworths, Washington, 1964) pp. 1?28.