2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/10284A review on some recent developments in gamma ray astrophysics with particular emphasis on the role of relativistic bulk motion in nonthermal gamma ray sources, radiation processes in AGN jets, high-energy neutrino astronomy and the use of gamma rays in the energy range 10 GeV - 50 TeV as a probe of the diffuse IR-UV radiation field at cosmic distances.31 pages compressed and uuencoded postscript; Rev. Mod. Astr., Vol.9Astrophysicstext