title: Why observational studies should be among the tools used in comparative effectiveness research.
authors.affiliation: Scientific Affairs, OutcomeSciences, Cambridge, Massachusetts, USA.
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Dreyer
authors.forename: Sean R
authors.initials: SR
authors.lastname: Tunis
authors.forename: Marc
authors.initials: M
authors.lastname: Berger
authors.forename: Dan
authors.initials: D
authors.lastname: Ollendorf
authors.forename: Pattra
authors.initials: P
authors.lastname: Mattox
authors.forename: Richard
authors.initials: R
authors.lastname: Gliklich