1. Ossaka, J., Advances in Clay Science, Proc. Second Ann. Meeting on Clay and Clay Minerals, 337 (1960).
2. Demeduk, T., and Cole, W. F., Nature, 181, 1400 (1958).
3. Scholze, H., Ber. D.K.G., 32, 381 (1955).
4. Agrell, S. O., and Smith, J. V., J. Amer. Ceramic Soc., 43, 69 (1960).