title: Comparative effectiveness reviews need to pay as much attention to external validity as to internal validity risks of bias.
authors.forename: Peter
authors.initials: P
authors.lastname: Tugwell
authors.forename: André
authors.initials: A
authors.lastname: Knottnerus
authors.forename: Leanne
authors.initials: L
authors.lastname: Idzerda
mesh_terms: D015982:Bias; D057186:Comparative Effectiveness Research; D015203:Reproducibility of Results; D012196:Review Literature as Topic