Cheosuwan, Thitirath, Somporn Saipanya, and Supan Tongphet. “The Improvement of a Quality Assurance Information Systems Based Six-Sigma Principles”. ECTI Transactions on Computer and Information Technology (ECTI-CIT) 11, no. 1 (April 11, 2017): 20–27. Accessed May 3, 2024. https://ph01.tci-thaijo.org/index.php/ecticit/article/view/66571.