2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/230883We prove the following theorem. Let $U$ be a pseudo-harmonic function on a surface $M^2$. For a real valued continuous function $V : M^2 \to {\mathbb R}$ to be a conjugate pseudo-harmonic function of $U$ on $M^2$ it is necessary and sufficient that $V$ is open on level sets of $U$.9 pages, 2 figuresGeometric TopologyComplex Variables54C10; 32Q55; 30F15text