1. For many details see T.J.M. Visser, Rheological properties of alkali borate glasses, Thesis Eindhoven, 1971.
2. P.J. Bray, J.G. O’Keefe, Phys. Chem. Glasses 4 37 (1963).
3. P. Beekenkamp, in Physics of Non-Crystalline Solids, J.A. Prins, ed., Amsterdam (1965) 512.
4. J.H. Li, D.R. Uhlmann, J. Non-Cryst. Solids 3 127, 205(1970).
5. H.R. Lillie, J. Am. Ceram. Soc. 16 619 (1933).