Sihombing, Juna, Adil Barus, Jahartap Yustin Pasaribu, and Immanuel Julius Sirait. 2025. “The Effectiveness of Activated Carbon Made from Shallot Skin in Reducing Calcium Levels and Total Hardness in Hard Water: Efektivitas Karbon Aktif Berbahan Kulit Bawang Merah Terhadap Penurunan Kadar Calsium Dan Total Hardness Pada Air Sadah”. Jurnal Rekayasa, Teknologi Proses Dan Sains Kimia (REPROKIMIA) 4 (1):38-43. https://doi.org/10.68115/reprokimia.v4i1.230.