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Examples A classic result in semigroup theory due to D. B. McAlister states that every inverse semigroup has an E-unitary cover ; besides being surjective , the homomorphism in this case is also idempotent separating , meaning that in its kernel an idempotent and non-idempotent never belong to the same equivalence class. ; something slightly stronger has actually be shown for inverse semigroups : every inverse semigroup admits an F-inverse cover .
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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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