Urry, C. M.; Scarpa, R.; O'Dowd, M.; Falomo, R.; Pesce, J. E.; Treves, A. (2000). »The Hubble Space Telescope Survey of BL Lacertae Objects. II. Host Galaxies«. The Astrophysical Journal. 532 (2): 816. arXiv:astro-ph/9911109. Bibcode:2000ApJ...532..816U. doi:10.1086/308616.
Urry, C. M.; Scarpa, R.; O'Dowd, M.; Falomo, R.; Pesce, J. E.; Treves, A. (2000). »The Hubble Space Telescope Survey of BL Lacertae Objects. II. Host Galaxies«. The Astrophysical Journal. 532 (2): 816. arXiv:astro-ph/9911109. Bibcode:2000ApJ...532..816U. doi:10.1086/308616.
Urry, C. M.; Scarpa, R.; O'Dowd, M.; Falomo, R.; Pesce, J. E.; Treves, A. (2000). »The Hubble Space Telescope Survey of BL Lacertae Objects. II. Host Galaxies«. The Astrophysical Journal. 532 (2): 816. arXiv:astro-ph/9911109. Bibcode:2000ApJ...532..816U. doi:10.1086/308616.