2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/227611We investigate cobordisms of free knots. Free knots and links are also called homotopy classes of Gauss words and phrases. We define a new strong invariant of free knots which allows to detect free knots not cobordant to the trivial one.10 pages, 19 figuresGeometric TopologyAlgebraic Geometrytext