2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/48968Recent results on second order quantum corrections to semileptonic decays of b quarks and positronium spectroscopy are reviewed. Similarities between calculations in these seemingly different problems are demonstrated. Technical aspects of solving systems of recurrence relations, and application of dimensional regularization to bound states are explained.Talk given at the 4th Intl. Symposium On Radiative Corrections, September 1998, Barcelona, Spain. 14 pages, latexHigh Energy Physics - Phenomenologytext