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On September 28 , 1976 , a declining Muhammad Ali defended his heavyweight crown against Ken Norton .
 person: Muhammad Ali; person: Ken Norton
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities: Muhammad Ali, Ken Norton 
Answer:
 person: Muhammad Ali; person: Ken Norton