1. Smith, D., Davis, P., and Brinker, C., Better Ceramics Through Chemistry IV, edited by Zelinski, B., Brinker, C., Clark, D., and Ulrich, D., (Materials Research Soc., v. 180, 1990), p. 235.
2. Room temperature gelation times can be as long as months at pH values near 2. See, for example, Ref. 12.
3. Pope, E. and Mackenzie, J., J. Non-Cryst. Solids 87, 185 (1986).
4. Coltrain, B., Melpolder, S., and Salvain, J., in Ultrastruct. Process. Adv. Mater., edited by Uhlmann, D. and Ulrich, D., (Wiley: New York, 1992), p. 69.
5. Sakka, S., Kozuka, H., and Kim, S.-H., Ultrastructure Processing of Advanced Ceramics edited by Mackenzie, J. and Ulrich, D., (Wiley: New York, 1988) p. 159.