Let R be a Krull domain
with fraction field K. Let L be a finite extension of K, and let S be the
integral closure of R in L; then S is also a Krull domain. Let 𝒫(R,S) be the
group of divisor classes in R becoming principal in S. Suppose there is a
group scheme (or Hopf algebra) acting on S with fixed ring R. Then there is
a cohomology group which contains 𝒫(R,S) and equals it if the action is
Galois at each minimal prime. This generalizes and unifies some results of
Samuel.