Creative Commons Attribution
['Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data.', 'Improved control of childhood asthma with low-dose, short-term vitamin D supplementation: a randomized, double-blind, placebo-controlled trial.', 'Iwona Stelmach', 'The BMJ', 'Creative Commons Attribution', 'Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data.']