Afriani F, J E, Zaitun, Tiandho Y. Improvement of Hardness of Hydroxyapatite by the Addition of Silica from Tin Tailings. JESR [Internet]. 2020Dec.28 [cited 2025Jun.23];2(2):85-9. Available from: http://jesr.eng.unila.ac.id/index.php/ojs/article/view/48