title: [Individual and group levels in population surveys and health services research].
authors.affiliation: Institutt for allmenn- og samfunnsmedisinske fag, Postboks 1130 Blindern, Universitetet i Oslo, 0317 Oslo. oyvind.nass@samfunnsmed.uio.no
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Naess
mesh_terms: D016021:Epidemiologic Studies; D004813:Epidemiology; D006302:Health Services Research; D006801:Humans; D011634:Public Health; D012107:Research Design