Wanapirak, C., T. Tongsong, P. Sirivatanapa, W. Piyamongkol, S. Sirirchotiyakul, A. Yampochai, A. Tuggapijit, and R. Sekararithi. “Midtrimester Amniocentesis : Experience of 2040 cases”. Thai Journal of Obstetrics and Gynaecology, vol. 9, no. 4, Dec. 1997, pp. 269-75, https://he02.tci-thaijo.org/index.php/tjog/article/view/257204.