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If $X$ is a space that can be mapped onto a metric space by a one-to-one mapping, then $X$ is said to have a weaker metric topology. In this paper, we give characterizations of sequence-covering compact images and sequentially-quotient compact images of spaces with a weaker metric topology. The main results are that (1) $Y$ is a sequence-covering compact image of a space with a weaker metric topology if and only if $Y$ has a sequence ${\left\{{ℱ}_i\right\}}_{i\in \mathbb{N}}$ of point-finite $cs$-covers such that ${\bigcap }_{i\in \mathbb{N}}\mathrm{st}(y,{ℱ}_i)=\left\{y\right\}$ for each $y\in Y$. (2) $Y$ is a sequentially-quotient...

The main purpose of this paper is to establish general conditions under which $T_2$-spaces are compact-covering images of metric spaces by using the concept of $cfp$-covers. We generalize a series of results on compact-covering open images and sequence-covering quotient images of metric spaces, and correct some mapping characterizations of $g$-metrizable spaces by compact-covering $\sigma$-maps and $mssc$-maps.

A topological space $X$ is called mesocompact (sequentially mesocompact) if for every open cover $𝒰$ of $X$, there exists an open refinement $𝒱$ of $𝒰$ such that $\{V\in 𝒱:V\cap K\ne \varnothing \}$ is finite for every compact set (converging sequence including its limit point) $K$ in $X$. In this paper, we give some characterizations of mesocompact (sequentially mesocompact) spaces using selection theory.