title: The critical role of observational evidence in comparative effectiveness research.
authors.affiliation: Evidence Review and Synthesis Practice, United BioSource Corporation, Bethesda, Maryland, USA. Rachael.fleurence@unitedbiosource.com
authors.forename: Rachael L
authors.initials: RL
authors.lastname: Fleurence
authors.forename: Huseyin
authors.initials: H
authors.lastname: Naci
authors.forename: Jeroen P
authors.initials: JP
authors.lastname: Jansen