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Racing career 1810 : three-year-old season Hephestion began his racing career on 23 April the opening day of the 1810 flat racing season at Newmarket Racecourse .
 Newmarket Racecourse
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Newmarket Racecourse