# Nguyen Van Dung

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Articles: 1

### $ls$-Ponomarev-systems and compact images of locally separable metric spaces

Methods Funct. Anal. Topology 15 (2009), no. 4, 391-400

We introduce the notion of an $ls$-Ponomarev-system $(f, M, X, \{\mathcal{P}_{\lambda,n}\})$, and give necessary and sufficient conditions such that the mapping $f$ is a compact (compact-covering, sequence-covering, pseudo-sequence-covering, sequentially-quotient) mapping from a locally separable metric space $M$ onto a space $X$. As applications of these results, we systematically get characterizations of certain compact images of locally separable metric spaces.
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