Tantiphanwadi, P., A. . Siripanya, P. . Panyakunanont, P. . Thanachotanankul, N. . Wongpatiwate, S. . Phwngmalay, and S. . Waiyanit. “Production Improvement Steps: Lean, Six Sigma and Lean Automation”. Naresuan University Engineering Journal, vol. 15, no. 2, Dec. 2020, pp. 47-64, https://ph01.tci-thaijo.org/index.php/nuej/article/view/240607.