Lecture Notes on Bayesian Estimation and Classification
《Lecture Notes on Bayesian Estimation and Classification》 · 第 28 页 · Section 1.5「Endomorphisms and Automorphisms」，小节「Characteristic and Fully-Invariant Subgroups」
A subgroup $H$ of a group $G$ is said to be fully-invariant in $G$ if $H^\alpha\le H$ for all $\alpha\in\operatorname{End}G$, and characteristic in $G$ if $H^\alpha\le H$ for all $\alpha\in\operatorname{Aut}G$.