1. V. A. Timofeeva, Kristallog. 9 (1964) 793.
2. M. M. Butcher and E. A. D. White, J. Amer. Ceram. Soc. 48 (1965) 492.
3. E. A. D. White and J. W. Brightwell, Chem. Ind. (London) 39 (1965) 1662.
4. J. D. C. Wood and E. A. D. White, J. Crystal Growth 3.4 (1968) 482.
5. C. A. Wallace and E. A. D. White, J. Phys. Chem. (Crystal Growth) Suppl. (1967) 431.