2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/84159Four-dimensional mass is determined in four-dimensional pseudo-Euclidean space as a physical invariant of that space. That invariant is discussed as an invariant of electromagnetic type. Finally, equations of Maxwell type are obtained for mass fields.3 pages, 1 figureGeneral Physicstext