Description: A surjective continuous open map maps second-countable spaces to second-countable spaces. (Contributed by Mario Carneiro, 9-Apr-2015)
Ref | Expression | ||
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Hypotheses | 2ndcomap.2 | |
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2ndcomap.3 | |
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2ndcomap.5 | |
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2ndcomap.6 | |
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2ndcomap.7 | |
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Assertion | 2ndcomap | |