Abraham, Irfan. “Penghitungan Efisiensi Pelatihan Dengan Return on Training Invesment”. Multidisciplinary Journal of Education , Economic and Culture 1, no. 2 (September 25, 2023): 95–102. Accessed September 28, 2024. https://sunanbonang.org/index.php/mjeec/article/view/125.