2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/122306Based on the notion of a $Δ$-group(oid), ring-valued invariants of pairs of topological spaces can be defined in intrinsic topological terms.5 pages, no figures, Theorem 1 has been removed, some corrections addedAlgebraic TopologyGroup Theory55P99text