2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/90640This talk is a survey of the question of joint measurability of coexistent observables and its is based on the monograph Operational Quantum Physics [1] and on the papers [2,3,4].A lecture presented at Quantum Composite Systems 2002, Ustron, Poland, 3.-7.9.2002Quantum Physicstext