(en) S. G. Engle, E. F. Guinan, G. M. Harper, H. R. Neilson et N. R. Evans, « The Secret Lives of Cepheids: Evolutionary Changes and Pulsation-induced Shock Heating in the Prototype Classical Cepheid δ Cep », The Astrophysical Journal, vol. 794, no 1, , p. 80 (DOI10.1088/0004-637X/794/1/80, Bibcode2014ApJ...794...80E, arXiv1409.8628)
(en) S. G. Engle, E. F. Guinan, G. M. Harper, H. R. Neilson et N. R. Evans, « The Secret Lives of Cepheids: Evolutionary Changes and Pulsation-induced Shock Heating in the Prototype Classical Cepheid δ Cep », The Astrophysical Journal, vol. 794, no 1, , p. 80 (DOI10.1088/0004-637X/794/1/80, Bibcode2014ApJ...794...80E, arXiv1409.8628)
(en) S. G. Engle, E. F. Guinan, G. M. Harper, H. R. Neilson et N. R. Evans, « The Secret Lives of Cepheids: Evolutionary Changes and Pulsation-induced Shock Heating in the Prototype Classical Cepheid δ Cep », The Astrophysical Journal, vol. 794, no 1, , p. 80 (DOI10.1088/0004-637X/794/1/80, Bibcode2014ApJ...794...80E, arXiv1409.8628)