Ketupanya, A., & Crandall, B. (1989). Comparison of Amniotic Fluid Alpha-Fetoprotein and Gel-Acetylcholinesterase Tests With Fetal Blood Contamination. Thai Journal of Obstetrics and Gynaecology, 1(1), 1–5. retrieved from https://he02.tci-thaijo.org/index.php/tjog/article/view/257912