title: Biases in the observational study of beta blockers in COPD.
authors.forename: S
authors.initials: S
authors.lastname: Suissa
authors.forename: P
authors.initials: P
authors.lastname: Ernst
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use*; D006801:Humans; D029424:Pulmonary Disease, Chronic Obstructive / Q000188:drug therapy*; D015983:Selection Bias
chemical_list: D000319:Adrenergic beta-Antagonists