Source: http://www.ests.um5.ac.ma/cours/Licence%20Professionnelle/Diagnostic%20et%20Maintenance%20des%20Syst%C3%A8mes/Semestre%2006/Outils%20de%20la%20qualit%C3%A9/Outils%20Qualit%C3%A9%20et%20Maintenance%20en%20milieu%20automobile.pdf