Class Field Theory
《Class Field Theory》 · 印刷第 41 页 Section 2.4「Further Properties of the Exponential」，Definition 2.13 完整定义
Definition 2.13. A function $A:\mathbb R\to\operatorname{GL}(n;\mathbb C)$ is called a one-parameter subgroup of $\operatorname{GL}(n;\mathbb C)$ if 1. $A$ is continuous, 2. $A(0)=I$, 3. $A(t+s)=A(t)A(s)$ for all $t,s\in\mathbb R$.