2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/97446We show that a Lorentzian homogeneous space admitting a homogeneous structure of type T1 + T3 is either a (locally) symmetric space or a singular homogeneous plane wave.7 pages, Latex2e, a small note and a reference addedDifferential GeometryHigh Energy Physics - Theory22F30text