| 21. | (The infimum is over all countable covers of"
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| 22. | This restricted set is countable and still forms a basis.
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| 23. | Thus it appears that " u " should be countable.
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| 24. | Contaminated sources may require dilution to achieve a " countable " membrane.
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| 25. | Every open set is a countable union of a collection of these.
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| 26. | We can imagine even larger ordinals that are still countable.
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| 27. | Every first-countable space is a Fr�chet Urysohn space.
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| 28. | Then A \ is a countable group containing C \.
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| 29. | It asserts that every strong measure zero set of reals is countable.
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| 30. | Every strong Fr�chet Urysohn space has strong countable fan tightness.
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