2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/42771We present Feynman rules for the strong and $ΔS = 1$ weak chiral Lagrangian which are relevant for calculating $K\to πππ$ decay amplitudes. Feynman rules for this specific case turn out to be too lengthy to be included in a research paper. Since they are not standard, we decide to include them in a separate article, making them available for any one who is interested in this kind of calculation. Any found mistakes and (/or) comments are warmly welcome so that corrections can be made.22 pagesHigh Energy Physics - Phenomenologytext