Jearranaikarn, Warinya, and Teera Siwadune. 2021. “A Comparison of Cervical Ruler and Transvaginal Ultrasound for Cervical Length Measurement during Pregnancy”. Thai Journal of Obstetrics and Gynaecology 29 (2). Bangkok, Thailand:65-72. https://doi.org/10.14456/tjog.2021.9.