1. D. Schott, D. Bloom, and H. Wise,J. Catalysis 6, 320 (1966).
2. N. E. Alekseevskii, G. E. Karstens, and V. V. Mozahev,Zh. Eksperim. i Teor. Fiz. 50, 1202 (1966) [English transl.,Soviet Phys.?JETP 23, 798 (1966)].
3. T. Tsuchida,J. Phys. Soc. Japan 18, 1016 (1963).
4. C. M. Hurd,J. Sci. Instr. 42, 465 (1965).
5. J. P. Jan, inSolid State Physics, F. Seitz and D. Turnbull, eds. (Academic Press, New York, 1957), Vol. V, p. 1.