1. Llewellyn Jones, F., and Parker, A. B., Nature, 165, 1960 (1950).
2. Llewellyn Jones, F., and Parker, A. B., Proc. Roy. Soc., A, 213, 185 (1952).
3. Dutton, J., Llewellyn Jones, F., and Palmer, R. W., Proc. Phys. Soc., 78, 569 (1961).
4. See, for example, Forrest, J. S., Howard, P. R., and Littler, D. J., Gas Discharges and the Electricity Supply Industry (Butterworth, London, 1962).
5. Raether, H., Electron Avalanches and Breakdown in Gases (Butterworth, London, 1964).