Six sigma advocacies were additionally used as a part of this paper.
Fulufhelo Ṋemavhola, Kemlall Ramdass 2017, 'USING STATISTICAL PROCESS CONTROL AND SIX SIGMA TO CRITICALLY ANALYSE SAFETY OF HELICALSPRINGS: A RAILWAY CASE STUDY', International Journal for Quality Researchhttp://www.ijqr.net/journal/v11-n3/9.pdf. Retrieved from DOAJ CC BY 4.0 (https://creativecommons.org/licenses/by-sa/4.0/legalcode)