Cited 7 times since 2020 (1.9 per year) source: EuropePMC American journal of respiratory and critical care medicine, Volume 202, Issue 3, 1 1 2020, Pages 312-313 Vitamin D Deficiency in Asthma and Chronic Obstructive Pulmonary Disease. A Chicken-or-Egg Story. Hiemstra PS, de Jongh RT