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In page Boris Spassky:

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Spassky's failure to qualify for the Portoroz Interzonal came after a last-round defeat at the hands of Mikhail Tal, in a nervy game in the 1958 Soviet championship,[3] held at Riga. Spassky had the advantage for much of the game, but missed a difficult win after adjournment, then declined a draw. A win would have qualified Spassky for the Interzonal, and a draw would have ensured a share of fourth place with Yuri Averbakh, with qualification possible via a playoff.[citation needed]