Remark 4.2.3.9. Let $f: X \rightarrow S$ be a morphism of simplicial sets. Then $f$ is a left covering map and only if the opposite morphism $f^{\operatorname{op}}: X^{\operatorname{op}} \rightarrow S^{\operatorname{op}}$ is a right covering map.
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$