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FILE - In this Aug. 11, 2016 file photo, United States' Michael Phelps celebrates winning the gold medal in the men's 200-meter individual medley during the swimming competitions at the 2016 Summer Olympics, in Rio de Janeiro, Brazil. (AP Photo/Lee Jin-man, File)

FILE - In this Aug. 11, 2016 file photo, United States' Michael Phelps celebrates winning the gold medal in the men's 200-meter individual medley during the swimming competitions at the 2016 Summer Olympics, in Rio de Janeiro, Brazil. (AP Photo/Lee Jin-man, File)

Michael Phelps

Olympic champion Michael Phelps has announced his intention to retire after the London Olympics.