1. Biedenharn, L. C., and Rose, M. E., Rev. Mod. Phys., 25, 729 (1953).
2. Russinov, L. I., and Chuykin, E. I., Doklady Akad. Nauk. U.S.S.R., 68, 1029 (1949). Ward, A. H., and Walker, D., Nature, 163, 168 (1949). Walter, M., Huber, O., and Zünti, W., Helv. Phys. Acta, 23, 697 (1950).
3. Phil. Mag., 44, 987 (1953).
4. Phil. Mag. (in the press).
5. Cf. a standard text in statistics, for example, Weatherburn, C. E. “A First Course in Mathematical Statistics” (Cambridge, 1946).