1. Butler, S. T., Nature (preceding communication); Austral. J. Sci., 26 (8) 236 (1964).
2. Butler, S. T., Phys. Rev., 80, 1095 (1950); 106, 272 (1957).
3. Pearson, C. A., and Butler, S. T., Phys. Rev. (in the press). One of the steps in the process seems to need more careful justification, as is obvious from the fact that for a purely real potential the right-hand side of equation (2) vanishes.
4. See, for example, Schiff, L. I., Quantum Mechanics (McGraw-Hill, N.Y., 1955), equations (19.15) and (19.26).
5. Macfarlane, M. H., and French, J. B., Rev. Mod. Phys., 32, 567 (1960).