Rashid, Muhammad Noman, et al. “SPUTUM CULTURE AND POLYMERASE CHAIN REACTION TESTS FOR IDENTIFICATION OF BACTERIAL PATHOGENS IN EXACERBATION OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE”. Pakistan Journal of Physiology, vol. 18, no. 1, Mar. 2022, pp. 39-43, https://pjp.pps.org.pk/index.php/PJP/article/view/1005.