1. P.A. I.Tahourdin: Oxford Report No. 36, U.K.A.E.A. Research Group, Atomic Energy Res. Estab. Harwell, BR 694, p. 2 (1946)
2. See [Ref. 5.1, p. 1]
3. E. W. Becker, K. Bier, H. Burghoff: Z. Naturforsch. 10a, 565–572 (1955)
4. E. W. Becker, R. Schütte: Z. Naturforsch. 11a, 679–680 (1956)
5. E. W. Becker: DBP 1096875, Filed Sept. 5, 1956, Patented July 6, 1961