title: The exception proves the rule.
authors.affiliation: Instituto Nacional de Silicosis, Hospital Universitario Central de Asturias, Facultad de Medicina, Oviedo, Asturias, España. Electronic address: pcasan@ins.es.
authors.forename: Pere
authors.initials: P
authors.lastname: Casan Clarà
mesh_terms: D006801:Humans; D008511:Medicine; D010825:Physics