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By 1990 , the governments of Bulgaria , Czechoslovakia , East Germany , Hungary , Poland and Romania , all of which had been imposed after World War II , were brought down as revolutions swept Eastern Europe .
 Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, Romania, Eastern Europe
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Bulgaria, Czechoslovakia, East Germany, Hungary, Poland, Romania, Eastern Europe