A. L., Shivaraj, Arun B. J., George A. D’Souza, and Niranjan Nagaraj. “A Clinical Study of Pulmonary Function Tests in Patients With COPD Exacerbation”. International Journal of Advances in Medicine 4, no. 6 (November 22, 2017): 1645–1648. Accessed March 19, 2025. https://www.ijmedicine.com/index.php/ijam/article/view/821.