2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/47953We review in brief the threshold expansion, a method to perform the expansion of Feynman integrals near the heavy quark-antiquark threshold, and its relation to the construction of two effective theories, non-relativistic QCD (NRQCD) and potential-NRQCD. We then summarize recent next-to-next-to-leading order results on the decay $J/Ψ\to l^+ l^-$, the bottom quark mass from $Υ$ sum rules and the top-anti-top production cross section near threshold in $e^+ e^-$ collisions.Talk presented at the XXXIIIrd Rencontres de Moriond `Electroweak Interactions and Unified Theories', 14-21 March 1998, Les Arcs, France; 12 pages, LaTeX, 1 figures, .sty files included, (v2): mistyped CF CA term in Eq. (12) fixedHigh Energy Physics - Phenomenologytext