Wannaprom, Napaporn, and Yaowalak Khanhuathon. “Development of Simple Device Based on Gas Diffusion With Natural Reagent Immobilized Paper and Digital Image Colorimetry for Ammonia Determination”. Journal of Applied Research on Science and Technology (JARST) 19, no. 1 (June 23, 2020): 86–96. Accessed May 2, 2024. https://ph01.tci-thaijo.org/index.php/rmutt-journal/article/view/240257.