Alehan, Dursun, et al. “Non-Invasive Evaluation of Aortic Regurgitation by Doppler Echocardiography in Children: Comparison With Contrast Angiography”. The Turkish Journal of Pediatrics, vol. 45, no. 1, Jan. 2003, pp. 15-20, https://turkjpediatr.org/article/view/2847.