2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/152287the main theorem gives a sufficient condition for a n elements of SL(2,R) to generate a free group.The idea behind it is to use a nonorientable version of the Dehn-Wolpert-Goldman twist and to sew it with the original representation of a free group to get representation of the closed surfase group and then to apply Goldman' theorem.amstexDifferential Geometrytext