2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/45352The $ππ$ interaction is studied at one loop order in the framework of Generalized Chiral Perturbation theoryCompressed+ uuencoded Postscript file, 13pages, 6 figures to appear in the 2nd ed. of the DAFNE Physics HandbookHigh Energy Physics - Phenomenologytext