Ibrahim, A., and G. Mohammad. “Right Ventricular Function in Patients With Pulmonary Hypertension; The Value of Myocardial Performance Index (Tei Index) Measured by Tissue Doppler Imaging”. Tishreen University Journal -Medical Sciences Series, vol. 39, no. 3, Sept. 2018, https://journal.tishreen.edu.sy/index.php/hlthscnc/article/view/3873.