2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/54991Talk at the International Workshop ``New Non Perturbative Methods and Quantization on the Light Cone", Les Houches February 24 - March 7, 1997.14 pages, RevTeXHigh Energy Physics - TheoryUnified Description and Canonical Reduction to Dirac's Observables of the Four Interactionstext