Boston Marathon

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Defending champion Wesley Korir, of Kenya, warms up prior to the start of the 117th running of the Boston Marathon, in Hopkinton, Mass., Monday, April 15, 2013. (AP Photo/Stew Milne)

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Wesley Korir (left) and Sharon Cherop, both of Kenya, kiss the winner's trophy after winning the men's and women's divisions of the 116th Boston Marathon in Boston on April 16, 2012. (Associated Press)

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Runners in Hopkinton, Mass., make their way across the starting line for the 116th running of the Boston Marathon on Monday, April 16, 2012. (AP Photo/Stew Milne)

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ASSOCIATED PRESS PHOTOGRAPHS Geoffrey Mutai of Kenya takes the final strides of the fastest marathon ever run in the men's division of the 115th Boston Marathon. Strong winds helped Mutai post a time of 2:03.02.

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Winner Geoffrey Mutai of Kenya crosses the finish line of the 115th Boston Marathon in Boston Monday, April 18, 2011. (AP Photo/Elise Amendola)

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Robert Kiprono Cheruiyot of Kenya, winner of men's elite division of the 2010 Boston Marathon, listens to reporter's question during a news conference for the 115th Boston Marathon, Friday, April 15, 2011, in Boston. The Boston Marathon is schedulted to run on Monday, April 18. (AP Photo/Bizuayehu Tesfaye)