2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/33451We employ a theorem due to Campbell to build some simple 4-dimensional cosmological models which originate from solutions describing waves propagating along the extra-dimension of a 5-dimensional Ricci-flat space. The dimensional reduction is performed in the Jordan frame according to the induced-matter theory of Wesson.7 pages, Latex2eGeneral Relativity and Quantum Cosmologytext