Description: The collection of all sets of the form F ( z ) = { y e. S | z C_ y } , which can be read as the set of all finite subsets of A which contain z as a subset, for each finite subset z of A , form a filter base. (Contributed by Mario Carneiro, 2-Sep-2015)
Ref | Expression | ||
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Hypotheses | tsmsfbas.s | |
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tsmsfbas.f | |
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tsmsfbas.l | |
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tsmsfbas.a | |
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Assertion | tsmsfbas | |