This is a classic example of Halton Arp's concept of how galaxy clusters form - note all 4 are in a strait line - no mention of location of this chain of Quasars - afraid someone might associate it with a closer galaxy!
http://www.mpg.de/9229786/quasar-quartet?filter_order=L&research_topic= http://www.haltonarp.com/articles/origins_of_quasars_and_galaxy_clusters Two of the best books by Arp on this subject: Seeing Red - Redshifts, Cosmology and Academic Science Catalogue of Discordant Redshift Associations
