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General Philippe Pétain declared the Ardennes to be " impenetrable " as long as " special provisions " were taken to destroy an invasion force as it emerged from the Ardennes by a pincer attack .
 Philippe Pétain, Ardennes, Ardennes
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Philippe Pétain, Ardennes, Ardennes