Kumar, A., Tandon, S., Nagdeote, S. T., Sharma, K., Shrikhande, A., & Gopal, K. (2017). Serum Vitamin D levels in Chronic Obstructive Pulmonary Disease. International Journal of Medical Research and Review, 5(2), 128-136. https://doi.org/10.17511/ijmrr.2017.i02.06