1. R. C. Vickery, Chemistry of the Lanthanons(Butterworth'sScientific Publications, London, 1953).
2. I. P. Kislyakov, Metallurgy of Rare Metals (in Russian] (Metallurgy Press, Moscow, 1957).
3. Rare Earth Metals [Russian translation] (IL, Moscow, 1957), edited by L. M. Komissarova and V. E. Plyushchev.
4. J. E. Campbell, High-temperature Technology (New York, 1956).
5. K. M. Smith and L. P. Doningnes, J. Amer. Ceram. Soc.37, 4 (1958).