title: Bias in observational studies of treatment.
authors.forename: D H
authors.initials: DH
authors.lastname: Osmond
authors.forename: E
authors.initials: E
authors.lastname: Charlebois
authors.forename: A R
authors.initials: AR
authors.lastname: Moss
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000188:drug therapy* / Q000401:mortality; D006801:Humans; D012107:Research Design; D015983:Selection Bias