2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/56442We review Kreimer's construction of a Hopf algebra associated to the Feynman graphs of a perturbative quantum field theory.11 pages, LaTeX2e, 11 eps figures. Published in `Quantum groups, noncommutative geometry and fundamental physical interactions', eds D. Kastler et al, Nova Science Publishers (1999) 233-242. (typos corrected and references updated; written in October 1998, somewhat out of date, but hopefully still useful)High Energy Physics - Theorytext