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Logical ambiguity and self-contradiction is analogous to visual ambiguity and impossible objects , such as the Necker cube and impossible cube , or many of the drawings of M. C. Escher .
 Necker, M. C. Escher
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Necker, M. C. Escher