Abstract:
In this paper, we answer two questions of P. Fletcher and W. Lindgren. We prove that a space $X$ is $wDelta$ and has a quasi--$G^*_{delta}$--diagonal if and only if it is developable, a space $X$ is $beta$--space with a quasi--$G^{*}_{delta}$--diagonal if and only if it is semi--stratifiable, a space $X$ is $beta$, quasi--$gamma$--space and has a quasi--$G^*_{delta}$--diagonal if and only if $X$ is developable and a space $X$ is metrizable if and only if it is paracompact $beta$--space with a quasi--$G_{delta}$--diagonal.