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He played at the tackle position for the University of Michigan from 1921 to 1923 , leading the Wolverines to consecutive undefeated seasons in 1922 and 1923 and a national championship in 1923 .
 University of Michigan, Wolverines
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 University of Michigan, Wolverines