Editing Threefold repetition (section)

===Fischer vs. Petrosian, 1971===
{{Chess diagram
|tright
|Fischer vs. Petrosian, 1971

|  |  |  |  |  |  |  |  
|pd|pd|  |  |  |pd|  |kd
|  |  |pd|  |  |qd|  |pd
|  |  |  |rd|  |pl|  |  
|  |  |  |  |  |rl|  |  
|  |  |  |  |  |  |  |pl
|pl|  |pl|  |ql|pl|  |  
|  |  |  |  |  |  |  |kl
|Position after 30.Qe2, 32.Qe2 and 34.Qe2
}}
In the third game<ref>{{cite web|url=http://www.chessgames.com/perl/chessgame?gid=1106921 |title=Fischer vs. Petrosian, 1971 |publisher=Chessgames.com |access-date=2020-07-03}}</ref> of the 1971 [[Candidates Tournament|Candidates Final Match]] in Buenos Aires between [[Bobby Fischer]] and [[Tigran Petrosian]], Petrosian (with a better position) accidentally allowed the position after 30.Qe2 ({{em|see diagram}}) to be repeated three times. Play continued:
:'''30... Qe5'''
:'''31. Qh5 Qf6''' 
31...Qxf4 32.Qxf7+ also leads to threefold repetition.
:'''32. Qe2''' (second time) '''Re5'''
:'''33. Qd3 Rd5?'''
and then Fischer wrote his next move
:'''34. Qe2''' (third time) '''½-½'''
on his {{chessgloss|scoresheet}}, which is the third appearance of the position with Black to move, and he claimed a draw.<ref>Different sources give different moves near the end. Plisetsky & Voronkov and Kasparov give 32...Re5 33.Qh5 Rd5. ChessGames.com and ''Chess Life'' (11/1971 and 12/1971) give 32...Re5 33.Qd3 Rd5.  The December 1971 ''Chess Life'' also discusses how the intermediate moves were different, and that Petrosian seemed unaware that he was going to allow a three-fold repetition.</ref> At first Petrosian was not aware of what was going on.  Incidentally, this was the first time a draw by threefold repetition had been claimed in his career.<ref>{{Harvcol|Plisetsky|Voronkov|2005|pp=283–84}}</ref><ref>{{Harvcol|Kasparov|2004|pp=422–23}}</ref><ref>{{Harvcol|Byrne|1971|p=682}}</ref>  This also illustrates that the intermediate moves do not need to be the same – just the positions.