Lueprasitsakul, W., P. Lueprasitsakul, P. Bangprathaiya, and P. Bhuripanyo. “Measurement of Serum Free Thyroxine by RIA in Normal Populations and During Pregnancy”. Srinagarind Medical Journal, vol. 4, no. 2, Nov. 2013, pp. 77-82, https://li01.tci-thaijo.org/index.php/SRIMEDJ/article/view/13486.