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However , after the event took place in 2012 , threats of future boycotts from some players , especially Rafael Nadal and Novak Djokovic ( who both lost on the blue surface ) , led the tournament to return to the traditional red clay for the 2013 season .
 person: Rafael Nadal; person: Novak Djokovic
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: Rafael Nadal, Novak Djokovic 
Answer:
 person: Rafael Nadal; person: Novak Djokovic