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Pedro Nuno Gonçalves Conceição Silva ( born January 21 , 1977 in Lisbon ) is a retired Portuguese swimmer , who specialized in sprint freestyle events .
 Pedro, Silva, Lisbon
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Pedro, Silva, Lisbon