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R. A. White, M. Bliton, S. Bhavsar, J. O. Bornmann, M. Ledlow et C. Loken, «A Catalog of Nearby Poor Clusters of Galaxies», Bulletin of the American Astronomical Society, vol.31, , p.979 (Bibcode1999AAS...194.8804W, lire en ligne[PDF])
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Abraham Mahtessian, «Groups of galaxies. III. Some empirical characteristics», Astrophysics, vol.41, no3, , p.308-321 (DOI10.1007/BF03036100, lire en ligne, consulté le )