title: Retrospective multipractice studies: problems involving attendance, design, and patients.
authors.forename: H T
authors.initials: HT
authors.lastname: Sørensen
authors.forename: F
authors.initials: F
authors.lastname: Olesen
mesh_terms: D002986:Clinical Trials as Topic; D006801:Humans; D010349:Patient Compliance; D012107:Research Design; D012189:Retrospective Studies