title: Quality assessment tools for observational studies: lack of consensus.
authors.forename: Shona
authors.initials: S
authors.lastname: Lang
authors.forename: Jos
authors.initials: J
authors.lastname: Kleijnen
mesh_terms: D032921:Consensus; D006801:Humans; D019370:Observation; D011786:Quality Control; D012107:Research Design / Q000592:standards*