Yohan Y. Analisis Kurva Kalibrasi Colorimeter Sederhana Penentuan Ammonium pada Sampel Pupuk NPK. PISTON J.Tech.Eng [Internet]. 2020 Jul. 15 [cited 2024 Dec. 22];4(1):42-7. Available from: https://openjournal.unpam.ac.id/index.php/Piston/article/view/7358