Ahmed, P., J. I. Bhat, S. Chaman, and A. A. Ahangar. “Serum Vitamin D Concentration in Acute Lower Respiratory Tract Infection in Infants: A Case Control Study from Northern India”. International Journal of Contemporary Pediatrics, vol. 4, no. 5, Aug. 2017, pp. 1772-4, doi:10.18203/2349-3291.ijcp20173783.