Kitipoonwongwanid, K., and A. Soongsatitanon. “Transvaginal Ultrasound Measurement of the Uterocervical Angle for Prediction of Spontaneous Preterm Birth”. Thai Journal of Obstetrics and Gynaecology, vol. 29, no. 2, Mar. 2021, pp. 112-9, doi:10.14456/tjog.2021.14.