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2. 2N. J. Zaluzec ; unpublished work.
3. 3E. M. Levin, C. R. Robbins, H. F. McMurdie, and M. K. Reser , Phase Diagrams for Ceramists , 1969, suppl. The American Ceramic Society, Inc., Columbus, Ohio; Fig.2313 .
4. 4T. M. Shaw , Ph.D. Thesis , University of California, Berkeley.