M. Stephan «Nebulæ (new) discovered and observed at the observatory of Marseilles, 1876 and 1877, M. Stephan». Monthly Notices of the Royal Astronomical Society, 37, 6, abril 1877, pàg. 334. Bibcode: 1877MNRAS..37..334S. DOI: 10.1093/mnras/37.6.334.
Hickson, Paul «Systematic properties of compact groups of galaxies». Astrophysical Journal, Part 1, 255, abril 1982, pàg. 382–391. Bibcode: 1982ApJ...255..382H. DOI: 10.1086/159838.
M. Stephan «Nebulæ (new) discovered and observed at the observatory of Marseilles, 1876 and 1877, M. Stephan». Monthly Notices of the Royal Astronomical Society, 37, 6, abril 1877, pàg. 334. Bibcode: 1877MNRAS..37..334S. DOI: 10.1093/mnras/37.6.334.
Hickson, Paul «Systematic properties of compact groups of galaxies». Astrophysical Journal, Part 1, 255, abril 1982, pàg. 382–391. Bibcode: 1982ApJ...255..382H. DOI: 10.1086/159838.