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During the difficult discussions in order to get a new government at the end of 2007 , Cathy Berx was a top staff member of Yves Leterme , who later became Prime Minister of Belgium .
 Cathy Berx, Yves Leterme
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Cathy Berx, Yves Leterme