22 August 2012
History of the World Championship on Fide.com
The Official site of the match for the title of World Chess Champion, aka the 2012 Anand - Gelfand match, has a good summary of World Championship title events: Match History. Perhaps unique among 'official' lists, it includes both FIDE and non-FIDE matches, as well as the final rounds of the knockout events. The Anand - Gelfand match would be the 52nd on the list.