Farooq, Muhammad Umer, et al. “Role of Low-Dose Theophylline on Functional Improvement in Patients of Moderately Severe Chronic Obstructive Pulmonary Disease”. Pakistan Armed Forces Medical Journal, vol. 73, no. 1, Mar. 2023, pp. 306-09, doi:10.51253/pafmj.v73i1.7254.