Fadhlilah, M., and D. Rochman. “Decrease in Operational Efficiency at PT X: Causes and Improvements With Lean Six Sigma DMAIC”. EKOMBIS REVIEW: Jurnal Ilmiah Ekonomi Dan Bisnis, Vol. 14, no. 3, July 2026, pp. 4239-54, doi:10.37676/ekombis.v14i3.10065.