^ 4.04.1Binggeli, B.; Sandage, A.; Tammann, G. A. Studies of the Virgo Cluster. II - A catalog of 2096 galaxies in the Virgo Cluster area. V - Luminosity functions of Virgo Cluster galaxies. The Astronomical Journal. September 1985, 90: 1681. Bibcode:1985AJ.....90.1681B. ISSN 0004-6256. doi:10.1086/113874(英语).