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Janko Tipsarević and Dušan Vemić were the defending champions , however they lost to František Čermák and Michal Mertiňák in the first round .
 Janko Tipsarević, Dušan Vemić, František Čermák, Michal Mertiňák
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Janko Tipsarević, Dušan Vemić, František Čermák, Michal Mertiňák