Shanmuganathan, A., A. G., M. N., R. R., N. Ganga, and P. K. “Correlation of Grade of Pulmonary Artery Pressure With Six Minutes Walk Distance and Dyspnoea Grading in Group 3 Pulmonary Artery Hypertension”. International Journal of Advances in Medicine, vol. 5, no. 2, Mar. 2018, pp. 343-50, doi:10.18203/2349-3933.ijam20180980.