Wimbledon 2012: Serena Williams into quarter-finals

Four-time Wimbledon champion Serena Williams comes through a testing match against Yaroslava Shvedova to reach the quarter-finals.

Williams' 6-1 2-6 7-5 victory sets up a last-eight meeting with defending champion Petra Kvitova, who beat Italy's Francesca Schiavone in three sets.

After the match, Williams insists she was not concerned by her form and is confident she can can play better.

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