Pasaribu, Betsy Tiurma, Siti Mujanah, and Achmad Yanu Alif Fianto. “Analysis of Lean Six Sigma Modeling in Efforts to Improve Operational Performance at Royal Surabaya Hospital”. International Journal of Economics (IJEC) 4, no. 1 (June 30, 2025): 682–693. Accessed December 5, 2025. https://ejournal.ipinternasional.com/index.php/ijec/article/view/1376.