L Thiruvarasu Letchumanan, Noordin Mohd Yusof, Hamed Gholami, and Nor Hasrul Akhmal Bin Ngadiman. “Green Lean Six Sigma: A Review”. 2021. Journal of Advanced Research in Technology and Innovation Management, vol. 1, no. 1, Sept. 2024, pp. 33-40, https://akademiabaru.com/submit/index.php/jartim/article/view/4398.