2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48925We discuss the field-theoretical approach to neutrino oscillations. This approach includes the neutrino source and detector processes and allows to obtain the neutrino transition or survival probabilities as cross sections derived from the Feynman diagram of the combined source -- detection process. In this context, the neutrinos which are supposed to oscillate appear as propagators of the neutrino mass eigenfields, connecting the source and detection processes.6 pages, revtex, talk presented by W. Grimus at WIN99, Capetown, South Africa, January 24-30, 1999High Energy Physics - Phenomenologytext