Girardi, M.; Barrena, R.; Boschin, W.; Ellingson, E. (tháng 11 năm 2008). “Cluster Abell 520: a perspective based on member galaxies. A cluster forming at the crossing of three filaments?”. Astronomy and Astrophysics. 491 (2): 379–395. arXiv:0809.3139. Bibcode:2008A&A...491..379G. doi:10.1051/0004-6361:200810549.
Girardi, M.; Barrena, R.; Boschin, W.; Ellingson, E. (tháng 11 năm 2008). “Cluster Abell 520: a perspective based on member galaxies. A cluster forming at the crossing of three filaments?”. Astronomy and Astrophysics. 491 (2): 379–395. arXiv:0809.3139. Bibcode:2008A&A...491..379G. doi:10.1051/0004-6361:200810549.
Girardi, M.; Barrena, R.; Boschin, W.; Ellingson, E. (tháng 11 năm 2008). “Cluster Abell 520: a perspective based on member galaxies. A cluster forming at the crossing of three filaments?”. Astronomy and Astrophysics. 491 (2): 379–395. arXiv:0809.3139. Bibcode:2008A&A...491..379G. doi:10.1051/0004-6361:200810549.