Yohan Y, Astuti F, Wicaksana A. Colorimeter Portable to Determine Ammonium Using to Manure Tetector. PISTON J.Tech.Eng [Internet]. 2021 Jan. 15 [cited 2024 Nov. 13];4(2):48-55. Available from: https://openjournal.unpam.ac.id/index.php/Piston/article/view/9617