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Trained with Bob Bowman , coach of American swimmer Michael Phelps , at the University of Michigan .
 Bob Bowman, Michael Phelps, University of Michigan
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Bob Bowman, Michael Phelps, University of Michigan