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The algebraic study of free groups was initiated by Jakob Nielsen in 1924 , who gave them their name and established many of their basic properties .
 person: Jakob Nielsen
Given options, please tell me the categories of all the listed entity words.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} 
 Entities: Jakob Nielsen 
Answer:
 person: Jakob Nielsen