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In mathematics , the Hitchin integrable system is an integrable system depending on the choice of a complex reductive group and a compact Riemann surface , introduced by Nigel Hitchin in 1987 .
 Hitchin, Nigel Hitchin
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Hitchin, Nigel Hitchin