2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/64910We give a formula for the Dixmier-Douady class of a continuous-trace groupoid crossed product that arises from an action of a locally trivial, proper, principal groupoid on a bundle of elementary $C^*$-algebras that satisfies Fell's condition.9 Pages, LaTeXOperator Algebras46L55text