1. Tyrén, F., Nova Ada Reg. Soc. Sci. Ops., iv, 12, No. 1 (1940). Flem-berg, H., Ark. f. Mat., Ast. Fys., 28 A, No. 18 (1942).
2. Eriksson, H. A. S., Z. Phys., 109, 762 (1938).
3. Lamb and Retherford, Phys. Rev., 72, 241 (1947).
4. Bethe, Phys. Rev., 72, 339 (1947).
5. Communicated at a meeting in Copenhagen, September 1947.