R., Prasuna K., Praveena Korani Ratnam, Pramod Kumar K. R., and Krishna Kumar T. V. K. “P Wave Axis and Its Correlation With Severity of Chronic Obstructive Pulmonary Disease”. International Journal of Advances in Medicine 7, no. 3 (February 24, 2020): 506–511. Accessed October 13, 2025. https://www.ijmedicine.com/index.php/ijam/article/view/2144.