title: Proof in observational medicine.
authors.affiliation: Department of Biomedical Sciences and Human Oncology, Main Hospital, Torino, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Vineis
mesh_terms: D015984:Causality; D006801:Humans; D008175:Lung Neoplasms / Q000209:etiology; D008962:Models, Theoretical; D019370:Observation; D010686:Philosophy, Medical; D016032:Randomized Controlled Trials as Topic; D012907:Smoking / Q000009:adverse effects