M. Sabri Mohamad Zin, A. Rahman Mahmood, W. Hasrulnizzam Wan Mahmood, and F. Rahim, “Six Sigma Analyze Phase for New Product Development Prototype Process Improvement”, IJET, vol. 7, no. 2.29, pp. 79–85, May 2018, doi: 10.14419/ijet.v7i2.29.13134.