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It escalated further with Slovenia 's blockade of Croatia 's EU accession from December 2008 until September – October 2009 , when Slovenia ( a European Union member state ) blocked the negotiation progress of Croatia ( an EU candidate state ) .
 Slovenia, Croatia, Slovenia, European Union, Croatia
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Slovenia, Croatia, Slovenia, European Union, Croatia