Using the Six Sigma methodology as an internal control system to improve the quality of the internal audit process: An analytical study of a sample opinions of the General Company for Fertilizers Industry - Southern Region employees. EJFB [Internet]. 2026 Mar. 29 [cited 2026 Jul. 21];7(1):89-101. Available from: https://ejfb.journalpath.com/ejfb/article/view/461