1. Andrew, E. R., Bradbury, A., and Eades, R. G., Colloque Ampère, Paris, July 11, 1958; Arch. Sci., 11, 223 (1958).
2. Andrew, E. R., Bradbury, A., and Eades, R. G., Nature, 182, 1659 (1958).
3. Andrew, E. R., and Newing, R. A., Proc. Phys. Soc., 72, 959 (1958).
4. Van Vleck, J. H., Phys. Rev., 74, 1168 (1948).
5. Andrew, E. R., Colloque Ampère, London, April 2, 1959.