Chaiyarach, Sukanya, Kiattisak Kongwattanakul, and Ratana Komwilaisak. 2021. “Ultrasound Uterine Cervical Angle Screening At Second Trimester to Predict Spontaneous Preterm Birth in Singleton Pregnancy”. Srinagarind Medical Journal 36 (5):522-26. https://li01.tci-thaijo.org/index.php/SRIMEDJ/article/view/252551.