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It is supplied by a number of major rivers , including the Danube , Dnieper , Southern Bug , Dniester , Don , and the Rioni .
 Danube, Dnieper, Southern Bug, Dniester, Don, Rioni
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Danube, Dnieper, Southern Bug, Dniester, Don, Rioni