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Vector calculus is initially defined for Euclidean 3-space , which has additional structure beyond simply being a 3-dimensional real vector space , namely : a norm ( giving a notion of length ) defined via an inner product ( the dot product ) , which in turn gives a notion of angle , and an orientation , which gives a notion of left-handed and right-handed .
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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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