1. Sletten, A. M., Nature, 183, 311 (1959).
2. Morant, M. J., paper read at the Durham conference of the Institute of Physics and the Physical Society on “Electronic Processes in Dielectric Liquids” (1963).
3. Brignell, J. E., thesis Univ. Lond. (1964).
4. Brignell, J. E., J. Sci. Instrum., 40, 576 (1963).
5. Lewis, T. J., Proc. Inst. Elec. Eng., 100, IIA, 141 (1953).