TY - JOUR AU - Bergman, P; Norlin, A C; Hansen, S TI - Vitamin D3 supplementation in patients with frequent respiratory tract infections: a randomised and double-blind intervention study JO - BMJ Open VL - 2. pii PY - 2012 DO - 10.1136/bmjopen-2012-001663 L3 - PubMed-ID: 23242238 SP - e001663 N1 - et al. ER -