S., M., Kumar, V., S., Y. and Reddy, V. 2017. Correlation of serum TNF alpha level with severity of chronic obstructive pulmonary disease. International Journal of Research in Medical Sciences. 5, 8 (Jul. 2017), 3309–3316. DOI:https://doi.org/10.18203/2320-6012.ijrms20173020.