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Allusions and references to current history , geography , and science The impeachment trial of President Douglass Dilman closely parallels that of President Andrew Johnson ( at the time the only Presidential impeachment proceedings to reach the articles stage , before Richard Nixon in 1974 and Bill Clinton in 1998 ) .
 person: Andrew Johnson; person: Richard Nixon; person: Bill Clinton
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: Andrew Johnson, Richard Nixon, Bill Clinton 
Answer:
 person: Andrew Johnson; person: Richard Nixon; person: Bill Clinton