Paul Adrien Maurice Dirac e Ralph Howard Fowler, The quantum theory of the electron, in Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, vol.117, n.778, 1997-01, pp.610–624, DOI:10.1098/rspa.1928.0023. URL consultato il 17 giugno 2025.
Paul Adrien Maurice Dirac e Ralph Howard Fowler, The quantum theory of the electron, in Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, vol.117, n.778, 1997-01, pp.610–624, DOI:10.1098/rspa.1928.0023. URL consultato il 17 giugno 2025.