1. J. Chadwick, Proc. Roy. Soc., A, 142, 1 (1933).
2. E. Fermi, and others, Proc. Roy. Soc., A, 146, 483 (1934); 149, 522 (1935).
3. Cf. N. Bohr, Faraday Lecture, J. Chem. Soc., 349 (1932), and W. Heisenberg, ” Zeeman Verhandelingen”, p. 108.
4. Fermi, and others, Proc. Roy. Soc., A, 149, 522 (1935). Perrin and Elsasser, J. Phys., 6, 195 (1935). Béthe, Phys. Rev., 47, 747 (1935).
5. Fermi and Amaldi, La Ricercio Scientifica, A, 6, 544 (1935), Szilard, NATURE, 136, 849 (1935). Frisch, Hevesy and McKay, NATURE, 137, 149 (1936).