Panutte, Wikanda, Nattaya Sae-ung, and Yupin Aniwat-angkoorn. 2018. “The Preparation of Standard Samples for Interlaboratory Proficiency Testing of HCG Pregnancy Test Kit in Medical Network”. Archives of Allied Health Sciences 30 (3). Khon Kaen, Thailand:289-99. https://he01.tci-thaijo.org/index.php/ams/article/view/163943.