K. Amris, E. E. Wæhrens, A. Stockmarr, H. Bliddal, and B. Danneskiold-Samsøe, “Factors influencing observed and self-reported functional ability in women with chronic widespread pain: a cross-sectional study”., JRM, vol. 46, no. 10, pp. 1014–1021, Jul. 2014.