Vitamin D status in patients with musculoskeletal pain, fatigue and headache:
Knutsen KV, Brekke M, Gjelstad S, Lagerløv P. Vitamin D status in patients with musculoskeletal pain, fatigue and headache: a cross-sectional descriptive study in a multi-ethnic general practice in Norway. Scand J Prim Health Care. 2010 Sep;28(3):166-71. doi: 10.3109/02813432.2010.505407.