1. P. Duwez, F. Odell andF. H. Brown Jr,J. Amer. Ceram. Soc. 35 (1952) 107.
2. A. Dietzel andH. Tober,Ber. Deut. Keram. Ges. 30 (1953) 71.
3. B. C. Weber, H. J. Garret, F. A. Maurer andM. A. Schwartz,J. Amer. Ceram. Soc. 39 (1956) 197.
4. S. Fernandes andL. Beaudin, presented at the 21st Annual Pittsburgh Diffraction Conference, Mellon Institute, Pittsburgh, Pennsylvania, November 1963.
5. R. Roy, H. Miyabe andA. M. Diness, presented at the 66th Annual Meeting of the American Ceramic Society, Chicago, April 21, 1964 (Basic Science Division No. 11-B-64); for abstract seeAmer. Ceram. Soc. Bull. 43 (1964) 255.