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During his time there , he worked with harmonica player Paul Butterfield and jammed with blues greats Muddy Waters , Howlin ' Wolf , and Buddy Guy , all of whom encouraged the young guitarist to pursue music .
 person: Paul Butterfield; person: Muddy Waters; person: Howlin ' Wolf; person: Buddy Guy
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 person: Paul Butterfield; person: Muddy Waters; person: Howlin ' Wolf; person: Buddy Guy