2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/231033Sturm oscillation theorem for second order differential equations was generalized to systems and higher order equations with positive leading coefficient by several authors. What we propose here is a Sturm oscillation theorem for systems of even order having strongly indefinite leading coefficient.9 pages. No figures. Fully revised version. To appear in Advanced Nonlinear StudiesClassical Analysis and ODEsFunctional Analysis58E10, 58J55, 53D12text