2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/61315A geometric interpretation is given for certain elliptic-hyperbolic systems in the plane. Among several examples, one which reduces in the elliptic region to the equations for harmonic 1-forms on the projective disc is studied in detail. A boundary-value problem for this example is formulated and is shown to possess weak solutions.20 pages, tcilatex; thoroughly revised, with new conditions, new discussion, and a revised proofAnalysis of PDEsDifferential Geometry35M10; 58J99text