2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/71061It is shown that the variational derivative of the integral of Branson's Q-curvature is the ambient obstruction tensor of Fefferman-Graham. A classification of irreducible conformally invariant tensors modulo quadratic and higher degree terms in curvature is established.12 pagesDifferential Geometry53B20text