PDF, "'Tuning Fork' Classification of Rich Clusters of Galaxies", Herbert J.Rood, Gummuluru N. Sastry, June 1971, doi:10.1086/129128, Bibcode: 1971PASP...83..313R (accessed 14 April 2010)
PDF, "'Tuning Fork' Classification of Rich Clusters of Galaxies", Herbert J.Rood, Gummuluru N. Sastry, June 1971, doi:10.1086/129128, Bibcode: 1971PASP...83..313R (accessed 14 April 2010)
PDF, "'Tuning Fork' Classification of Rich Clusters of Galaxies", Herbert J.Rood, Gummuluru N. Sastry, June 1971, doi:10.1086/129128, Bibcode: 1971PASP...83..313R (accessed 14 April 2010)
COSMOS - The SAO Encyclopedia of Astronomy, "CD Galaxies"Архивная копия от 21 марта 2012 на Wayback Machine, Swinburne University of Technology (accessed 14 April 2010)
COSMOS - The SAO Encyclopedia of Astronomy, "CD Galaxies"Архивная копия от 21 марта 2012 на Wayback Machine, Swinburne University of Technology (accessed 14 April 2010)