“Model Semivariogram dalam Menaksir Sebaran Kadar Ni Menggunakan Metode Ordinary Kriging (Studi Kasus Endapan Nikel Laterit di PT Vale Indonesia Tbk)”. SPECTA Journal of Technology 6, no. 1 (April 25, 2022): 55–67. Diakses November 1, 2026. https://journal.itk.ac.id/index.php/sjt/article/view/697.