Lecture Notes on Bayesian Estimation and Classification
《Lecture Notes on Bayesian Estimation and Classification》 · 第 68 页 · Section 3.1「Series and Composition Series」
A group $G$ is said to be an extension of a group $N$ by a group $Q$ if there exists $M\trianglelefteq G$ such that $M\cong N$ and $G/M\cong Q$.