1. F. R. Charvat and R. M. Youmans, Bull. Amer. Ceram. Soc. 44 (1965) 409.
2. W. Bardsley and B. Cockayne, Crystal Growth (Suppl. to J. Phys. Chem. Sol.) (1967) 109.
3. J. Basterfield, M. J. Prescott, and B. Cockayne, J. Materials Sci. 3 (1968) 33.
4. F. R. Charvat, J. C. Smith, and O. H. Nestor, Crystal Growth (Suppl. to J. Phys. Chem. Sol.) (1967) 45.
5. B. Cockayne, M. Chesswas, and D. B. Gasson, J. Materials Sci. 3 (1968) 224.