2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/206519We present a construction of string--localized covariant free quantum fields for a large class of irreducible (ray) representations of the Poincare group. Among these are the representations of mass zero and infinite spin, which are known to be incompatible with point-like localized fields. (Based on joint work with B.Schroer and J.Yngvason [13].)16 pages; Submitted to the proceedings of the symposium in honour of Jaques Bros, Paris 2004High Energy Physics - Theorytext