1. D. T. Livey andP. Murray, Plansee Proc., Ind. Seminar (Reutte/Tyrol, 1955) p. 375 (published 1956).
2. R. D. Carnahan, T. L. Johnson, andC. H. Li,J. Amer. Ceram. Soc. 41 (1958) 343.
3. W. M. Wolf, A. P. Levitt, andJ. Brown,Chem. Eng. Progr. 62 (1966) 74.
4. C. F. Morel,J. Sci. Instr. 43 (1966) 647.
5. W. H. Sutton, Report R64SD44, GE Space Science Laboratory (Philadelphia, USA, 1964).