Dirac, Paul Adrien Maurice (1927). “The quantum theory of the emission and absorption of radiation”. 《Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character》 114 (767): 243–265. Bibcode:1927RSPSA.114..243D. doi:10.1098/rspa.1927.0039.
Dirac, Paul Adrien Maurice (1927). “The quantum theory of the emission and absorption of radiation”. 《Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character》 114 (767): 243–265. Bibcode:1927RSPSA.114..243D. doi:10.1098/rspa.1927.0039.