Lecture Notes on Bayesian Estimation and Classification
《Lecture Notes on Bayesian Estimation and Classification》 · 第 145 页 · Section 5.3「Groups of Prime-Power Order」，小节「Central Products」
More generally a group $G$ is said to be the central product of its normal subgroups $G_1,\ldots,G_n$ if $G=G_1G_2\cdots G_n$, $[G_i,G_j]=1$ for $i\neq j$, and $G_i\cap\prod_{j\neq i}G_j=\zeta G$ for all $i$.