1. J. Chadwick, “Possible Existence of a Neutron,” Nature 129 (1932), 312; idem., “The Existence of a Neutron,” Proc. Roy. Soc. A136 (1932), 692–708; C.D. Anderson, “The Apparent Existence of Easily Deflectable Positives,” Science 76 (1933), 238–239; idem., “The Positive Electron,” Phys. Rev. 43 (1933), 491–494; H.C. Urey, F.G. Brickwedde, and G.M. Murphy, “A Hydrogen Isotope of Mass 2,” Phys. Rev. 39 (1932), 164–165. The spectroscopic discovery of heavy hydrogen was first reported by Harold Urey at a meeting of the American Physical Society at Tulane University, 28–30 December 1931. See also J.D. Cockcroft and E.T.S. Walton, “Disintegration of Lithium by Swift Protons,” Nature 129 (1932), 649.
2. C. Werner, “1932 – Moving into the New Physics,” Physics Today 25 (May 1972), 40–49.
3. For a historical account of Gamow’s theory of alpha decay, see R.H. Stuewer, “Gamow’s Theory of Alpha Decay,” in The Kaleidoscope of Science: The Israel Colloquium Studies in History, Philosophy, and Sociology of Science, E. Ullmann-Margalit (ed.) (Dordrecht: Reidel, 1986), pp. 147–186.
4. Bohr to Heisenberg, December 1928, BSC (11.2); the translation has been taken from BCW, Vol. 6, Foundations of Quantum Physics I (1926–1932), Jurgen Kalckar (ed.) (Amsterdam: North-Holland, 1985), pp. 24–25.
5. For a thorough discussion of the difficulties of the nuclear-electron hypothesis, and for references, see R.H. Stuewer, “The Nuclear Electron Hypothesis,” in Otto Hahn and the Rise of Nuclear Physics, W.R. Shea (ed.) (Dordrecht: Reidel, 1983), pp. 19–67.