Abstract Algebra
《Abstract Algebra》 · 第 179 页 · Section 5.5「Semidirect Products」
For $H$ any group let $K=\operatorname{Aut}(H)$ with $\varphi$ the identity map from $K$ to $\operatorname{Aut}(H)$. The semidirect product $H\rtimes\operatorname{Aut}(H)$ is called the holomorph of $H$ and will be denoted by $\operatorname{Hol}(H)$.