Wanapirak, C., and S. Chaijaroen. “Doppler Index for Prediction of Benign and Malignant Ovarian Tumour”. Thai Journal of Obstetrics and Gynaecology, vol. 9, no. 3, Sept. 1997, pp. 213-8, https://he02.tci-thaijo.org/index.php/tjog/article/view/257250.