2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/45553I investigate the bound state problems of lowest-lying mesons and heavy mesons. Chiral symmetry is essential when one consider lowest-lying mesons. Heavy quark symmetry plays an central role in considering the semi-leptonic form factors of heavy mesons. Various properties based on the symmetries are revealed using Bethe-Salpeter equations.86 pages + 15 uuencoded eps and ps figures, LaTeXHigh Energy Physics - Phenomenologytext