1. L.T. Aldrich et al., (eds.), Cosmological and Geological Implications of Isotope Ratio Variations. Nuclear Science Series, Report 23. (National Research Council, Washington, DC, 1958)
2. E. Amaldi, The Adventurous Life of Friedrich Georg Houtermans, Physicist (1903–1996) (Springer, Berlin, 2012)
3. F.L. Arnot, Cosmological theory. Nature 141, 1142–1143 (1938)
4. F.L. Arnot, Time and the Universe (Australasian Medical Publishing, Sydney, 1941)
5. V. Bargmann, Relativity. Rev. Mod. Phys. 29, 161–174 (1957)