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When Felix Klein wrote his book on non-Euclidean geometry in 1928 , he provided a foundation for the subject by reference to projective geometry .
 person: Felix Klein
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: Felix Klein 
Answer:
 person: Felix Klein