Description: Lemma for alexsubALT . If a point is covered by a collection taken from the base with no finite subcover, a set from the subbase can be added that covers the point so that the resulting collection has no finite subcover. (Contributed by Jeff Hankins, 28-Jan-2010) (Revised by Mario Carneiro, 14-Dec-2013)
Ref | Expression | ||
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Hypothesis | alexsubALT.1 | |
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Assertion | alexsubALTlem3 | |