M. Stephan (April 1877). "Nebulæ (new) discovered and observed at the observatory of Marseilles, 1876 and 1877, M. Stephan". Monthly Notices of the Royal Astronomical Society37: 334. Bibcode:1877MNRAS..37..334S. doi:10.1093/mnras/37.6.334.
Hickson, Paul (April 1982). "Systematic properties of compact groups of galaxies". Astrophysical Journal, Part 1255: 382–391. Bibcode:1982ApJ...255..382H. doi:10.1086/159838.
M. Stephan (April 1877). "Nebulæ (new) discovered and observed at the observatory of Marseilles, 1876 and 1877, M. Stephan". Monthly Notices of the Royal Astronomical Society37: 334. Bibcode:1877MNRAS..37..334S. doi:10.1093/mnras/37.6.334.
Hickson, Paul (April 1982). "Systematic properties of compact groups of galaxies". Astrophysical Journal, Part 1255: 382–391. Bibcode:1982ApJ...255..382H. doi:10.1086/159838.