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Mathematician Donald Crowe has analyzed , in particular , the two-dimensional designs of Benin , Yoruba and Kuba arts and has shown the extent of the Africans ' explorations into the formal possibilities of geometric variation .
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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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