Vachirasrisoontra, C., Anansakunwat, W., Hangchaowanit, Y., Indrambarya, J., Chantrapitak, W., Sritippayawan, S., Chantapakul, M., Srichantuek, K. and Suthantikorn, C. (2000) “Maternal Serum Free Beta-Human Chorionic Gonadotropin Levels between 14 and 21 Weeks of Gestation in Thai Pregnant Women”, Thai Journal of Obstetrics and Gynaecology. Bangkok, Thailand, 12(4), pp. 283–289. available at: https://he02.tci-thaijo.org/index.php/tjog/article/view/256949 (accessed: 30 September 2026).