Local Fields
《Local Fields》 · 第 24 页 · Chapter I，Section 7「Galois Extensions」，Artin symbol
If $G(L/K)$ is abelian, the Frobenius automorphism depends only on $\mathfrak p$; it is denoted by $(\mathfrak p,L/K)$ and is called the Artin symbol. The symbol is extended multiplicatively to ideals prime to the ramified primes.