2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/171881Let G be a graph. It was proved that if G is a planar graph without {4, 6, 7}-cycles and without two 5-cycles sharing exactly one edge, then G 3-colorable. We observed that the proof of this result is not correct.2 pagesCombinatoricstext