1. R.G. Chambers, Proc Roy. Soc, Vol. A 215, p. 481 (1952).
2. G. Reuter and E.H. Sondheimer, Proc, Roy. Soc., Vol, A 195, p. 336 (1948).
3. A. B. Pippard, Proc,. Roy. Soc., Vol. A 191. p. 870 (1947).
4. L. Simon, Tech. Rept. No. 126, Research Lab, of Electronics, MIT.
5. W.M. Failbank, Phys. Rev., Vol. 74 p. 1106 (1949).