2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/8875This paper summarizes recent developments in the study of the propagation of ultra-high energy cosmic ray protons or nuclei in the Universe, with emphasis on the consequences of energy losses and on the influence of extra-galactic magnetic fields.proceedings of "5th Rencontres du Vietnam - New views on the Universe", Hanoi, Aug.5-11, 2004Astrophysicstext