2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/96169We prove a version of Knebusch's Norm Principle for finite étale extensions of semi-local Noetherian domains with infinite residue fields of characteristic different from 2. As an application we prove Grothendieck's conjecture on principal homogeneous spaces for the spinor group of a quadratic space.14 pages, hyperref, xypic, (This is an extended and revised version of the previous preprint: The proof of Grothendieck's conjecture on Principal Homogeneous Spaces for the case of spinor group was added)Algebraic GeometryCommutative Algebra20G35; 13H05text