Algebraic Number Theory
《Algebraic Number Theory》 · 第 302 页 · Chapter IV，Section 6「The General Reciprocity Law」
The inverse of the mapping $r_{L/K}:G(L/K)^{\mathrm{ab}}\to A_K/N_{L/K}A_L$ gives, for every finite Galois extension $L/K$, a surjective homomorphism $(\ ,L/K):A_K\twoheadrightarrow G(L/K)^{\mathrm{ab}}$ with kernel $N_{L/K}A_L$. This map is called the norm residue symbol of $L/K$.