The Australian Open

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Ana Ivanovic of Serbia celebrates her win over Serena Williams of the U.S. in their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Sunday, Jan. 19, 2014.(AP Photo/Andrew Brownbill)

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Tomas Berdych of the Czech Republic serves to Kevin Anderson of South Africa during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Sunday, Jan. 19, 2014.(AP Photo/Aaron Favila)

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Ana Ivanovic of Serbia celebrates her win over Serena Williams of the U.S. during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Sunday, Jan. 19, 2014.(AP Photo/Aaron Favila)

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Ana Ivanovic of Serbia, left, is congratulated by Serena Williams of the U.S. after Ivanovic's fourth round win at the Australian Open tennis championship in Melbourne, Australia, Sunday, Jan. 19, 2014.(AP Photo/Aaron Favila)

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Serena Williams of the U.S. rests on her racket during her fourth round loss to Ana Ivanovic of Serbia at the Australian Open tennis championship in Melbourne, Australia, Sunday, Jan. 19, 2014.(AP Photo/Aaron Favila)

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Casey Dellacqua of Australia makes a backhand return to Eugenie Bouchard of Canada during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Sunday, Jan. 19, 2014.(AP Photo/Rick Rycroft)

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Eugenie Bouchard of Canada makes a forehand return to Casey Dellacqua of Australia during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Sunday, Jan. 19, 2014.(AP Photo/Aijaz Rahi)

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Flavia Pennetta of Italy celebrates after winning over Angelique Kerber of Germany during their fourth round match at the Australian Open tennis championship in Melbourne, Australia, Sunday, Jan. 19, 2014.(AP Photo/Eugene Hoshiko)