Compact Lie Groups
《Compact Lie Groups》 · 第 485 页 · Section 6.1「Finite Abelian Groups」末段
An abelian group $G$ is finitely generated if there are finitely many elements $a_1,\ldots,a_n\in G$ so that every $x\in G$ is a linear combination of them: $x=\sum_i m_i a_i$, where $m_i\in\mathbb Z$ for all $i$.