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The type theory was initially created to avoid paradoxes in a variety of formal logic s and rewrite system s. Later , type theory referred to a class of formal systems , some of which can serve as alternatives to naive set theory as a foundation for all mathematics .
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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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