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He collaborated on such cartoons as " Donald 's Nephews " ( 1938 ) , " Donald 's Cousin Gus " ( 1939 ) , " Mr. Duck Steps Out " ( 1940 ) , " Timber " ( 1941 ) , " The Vanishing Private " ( 1942 ) and " The Plastics Inventor " ( 1944 ) .
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Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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