Norm of an integral element over a normal domain ($N_{L/K}(b)\in A$)

Let $A$ be an integrally closed domain with fraction field $K$, and let $L/K$ be finite. If $b\in L$ is an integral element over $A$, its monic minimal polynomial lies in $A[T]$: its roots are integral, so its coefficients are integral elements of $K$, hence belong to $A$. If that polynomial has degree $r$ and constant coefficient $a_0$, then $N_{L/K}(b)=((-1{)}^r{a}_0{)}^{[L:K(b)]}\in A$. This remains true for inseparable extensions. An infinite algebraic extension has no usual determinant field norm.