2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/191615The physical meaning of bare and dressed scattering matrix singularities has been investigated. Special attention has been attributed to the role of well known invariance of scattering matrix with respect to the field transformation of the effective Lagrangian. Examples of evaluating bare and dressed quantities in various models are given.14 pages, Summary of the BRAG2007 workshopHigh Energy Physics - PhenomenologyNuclear Theorytext