2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/36735Selected topics on precision tests of the Standard Model of the Electroweak and the Strong Interaction at the LEP $e^+e^-$ collider are presented, including an update of the world summary of measurements of $α_s$, representing the state of knowledge of summer 1999. This write-up of lecture notes consists of a reproduction of slides, pictures and tables, supplemented by a short descriptive text and a list of relevant references.lecture given at Intern. Summer School at Nijmegen, August 1999, 44 pages, 36 (mostly coloured) figures, LaTeX, needs crckapb.styHigh Energy Physics - ExperimentHigh Energy Physics - Phenomenologytext