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From its beginnings , the activities of the Kunstverein Winterthur were monitoring " contemporary art " - then Impressionism , Post-Impressionism and especially Les Nabis , up to post-WWII and nowadays most recent positions like Richard Hamilton , Mario Merz and Gerhard Richter .
 Winterthur, Richard Hamilton, Mario Merz, Gerhard Richter
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Winterthur, Richard Hamilton, Mario Merz, Gerhard Richter