2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/33412The theorem on the existence of three commuting contractions on a Hilbert space and of a linear homogeneous matrix function of three independent variables for which the generalized von Neumann inequality fails is proved.6 pages, LaTeX 2.09Functional AnalysisOperator Algebrastext