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During the 1930 s and 1940 s , Joseph Stalin 's NKVD carried out numerous assassinations outside of the Soviet Union , such as the killings of Organization of Ukrainian Nationalists leader Yevhen Konovalets , Ignace Poretsky , Fourth International secretary Rudolf Klement , Leon Trotsky , and the Workers ' Party of Marxist Unification ( POUM ) leadership in Catalonia .
 Joseph Stalin, NKVD, Soviet Union, Organization of Ukrainian Nationalists, Yevhen Konovalets, Ignace Poretsky, Fourth International, Rudolf Klement, Leon Trotsky, Workers ' Party of Marxist Unification, POUM, Catalonia
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Joseph Stalin, NKVD, Soviet Union, Organization of Ukrainian Nationalists, Yevhen Konovalets, Ignace Poretsky, Fourth International, Rudolf Klement, Leon Trotsky, Workers ' Party of Marxist Unification, POUM, Catalonia