Kansiz , T. ., H. . Ayoglu, . B. G. . Aydin, R. D. . Okyay, G. . Kucukosman, H. . Oztoprak, and O. . Piskin. “The Efficacy of Inferior Vena Cava Diameter, Perfusion Index and Pleth Variability Index on Predicting Hypotension in Spinal Anesthesia”. Annals of Medical Research, vol. 29, no. 6, June 2022, pp. 616-22, http://www.annalsmedres.org/index.php/aomr/article/view/4192.