Iftikhar Ali Kakar, Abdul Baqi, Nasir Azim, Hafsa Rafiq, Iqra Lodhi, Khalid Shahab. “Pulmonary Arterial Hypertension in COPD and Its Correlation With Disease Severity”. Pakistan Journal of Medical & Health Sciences, vol. 16, no. 12, Feb. 2023, p. 391, doi:10.53350/pjmhs20221612391.