1. I. Sawai, Glass Technol. 2 (1961) 243.
2. J. Williamson, A. J. Tipple, and P. S. Rogers, J. Iron Steel Inst. 206 (1968) 898.
3. P. S. Rogers and J. Williamson, Glass Technol. 10 (1969) 128.
4. K. Seal, J. Soc. Glass Technol. 32 (1948) 46.
5. W. D. Johnston, J. Amer. Ceram. Soc. 48 (1965) 608.