Anjum, Naveed, et al. “COMPARISON OF CLINICAL CURE RATE FOR DOXYCYCLINE AND LEVOFLOXACIN IN TREATMENT OF ACUTE EXACERBATION OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE”. Pakistan Armed Forces Medical Journal, vol. 69, no. 6, Dec. 2019, pp. 1238-42, https://pafmj.org/PAFMJ/article/view/3642.