(1)
Sihombing, J.; Barus, A. .; Pasaribu, J. Y.; Sirait, I. J. 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. REPROKIMIA 2025, 4, 38-43.