1. Galea S, Tracy M: Participation rates in epidemiologic studies. Ann Epidemiol. 2007, 17 (9): 643-653. 10.1016/j.annepidem.2007.03.013.
2. Holmen J, Midthjell K, Forsen L, Skjerve K, Gorseth M, Oseland A: A health survey in Nord-Trondelag 1984-86. Participation and comparison of attendants and non-attendants. Tidsskr Nor Laegeforen. 1990, 110 (15): 1973-1977.
3. Holmen J, Midthjell K, Kruger O, Langhammer A, Holmen T, Bratberg GH, et al: The Nord-Trøndelag Health Study 1995-97 (HUNT2): objectives, contents, methods and participation. Norwegian Journal of Epidemiology. 2003, 13 (1): 19-32. Available from:
http://www.ntnu.no/c/document_library/get_file?uuid=880d3372-dabc-404b-ba61-e1d27cb5bb09&groupId=10304
4. Krokstad S, Langhammer A, Hveem K, Holmen T, Midthjell K, Stene T, et al: Cohort profile: the HUNT Study, Norway. Int J Epidemiol. 2012, Aug 9. [Epub ahead of print]
5. Knudsen AK, Hotopf M, Skogen JC, Overland S, Mykletun A: The health status of nonparticipants in a population-based health study: the Hordaland Health Study. Am J Epidemiol. 2010, 172 (11): 1306-1314. 10.1093/aje/kwq257.