2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/59192Stated lemma contains the assertions about isomorphism of exact m-forms and exterior differentials of regular m-maps, of linearly harmonic m-forms and exterior differentials of regular harmonic m-maps, of global minimal (n-m)-surfaces and level (n-m)-surfaces of regular minimal m-maps. It hold in n-dimensional Euclidean space.PostScript, 2 pagesGeneral Mathematicstext