Opsal, A., Kristensen, Øistein, Ruud, T., Larsen, T.K., Gråwe, R.W. and Clausen, T. 2011. Substance abuse in patients admitted voluntarily and involuntarily to acute psychiatric wards: a national cross-sectional study. Norsk Epidemiologi. 21, 1 (Dec. 2011). DOI:https://doi.org/10.5324/nje.v21i1.1430.