1. I. H. Pratt, National Electronics Conference Chicago Proceedings Vol. 20, 215 (1964).
2. G. K. Wehner and R. V. Stuart, 23rd Annual Conference Physical Electronics MIT, Cambridge, Mass., March 1963, Report p. 150 and in CR VI Conf. Internat. Phenomenes d’Ionization dans les Gaz (Paris 1963 ), Vol. 2, p. 49;
3. R. V. Stuart, K. Brower and W. Mayer, Rev. Sci. Instr. 34, 425 (1963);
4. R. V. Stuart and G. K. Wehner, J. Appl. Phys. 35, 1819 (1964).
5. H. M. Smith and A. F. Turner, Appl. Opt. 4, 147 (1965).