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# Article

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Keywords:
$\aleph$-space; $k$-network; closed map; countably bi-quotient map
Summary:
In this paper we improve some mapping theorems on $\aleph$-spaces. For instance we show that an $\aleph$-space is preserved by a closed and countably bi-quotient map. This is an improvement of Yun Ziqiu's theorem: an $\aleph$-space is preserved by a closed and open map.
References:
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