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He studied with drummer Alan Dawson at an early age , and began playing professionally at the age of 13 with saxophonist Sam Rivers .
 person: Alan Dawson; person: Sam Rivers
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: Alan Dawson; person: Sam Rivers