Mukdee, C., T. Suntharasaj, and C. Petpichetchian. “Prediction of Successful Normal Vaginal Delivery by Ultrasonographic Measurement of Occiput-spine Angle during First Stage of Labor”. Thai Journal of Obstetrics and Gynaecology, vol. 29, no. 5, Sept. 2021, pp. 288-97, doi:10.14456/tjog.2021.34.