1. Jones, J. B., Sanders, J. V., and Segnit, E. R., Nature, 204, 990 (1964).
2. Sanders, J. V., Nature, 204, 1151 (1964).
3. Bechtold, M. F., and Snyder, O. E., U.S. Patent 2,574,902 (E. I. du Pont de Nemours and Co., 1951).
4. Iler, R. K., The Colloid Chemistry of Silica and Silicates, 95 (Cornell Univ. Press, Ithaca, N.Y., 1955).
5. Iler, R. K., The Colloid Chemistry of Silica and Silicates, 133 (Cornell Univ. Press, Ithaca, N.Y., 1955).