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name: Finite $T_0$-spaces and universal mappings. (Holsztyński, Pedersen)
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A space for which every collection of open sets has a minimal element.
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Every nonempty collection of open sets has a minimal element.
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Equivalently:
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- Every collection of closed sets has a maximal element.
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- Every nonempty collection of closed sets has a maximal element.
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- The open sets satisfy the *descending chain condition*: There is no infinite strictly decreasing sequence $O_1 \supsetneq O_2 \supsetneq \cdots$ of open sets.
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- The closed sets satisfy the *ascending chain condition*: There is no infinite strictly increasing sequence $Y_1 \subsetneq Y_2 \subsetneq \cdots$ of closed sets.
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