Source: http://www.devoir.tn/secondaire/Doc/4-%C3%A8me-ann%C3%A9es/Techniques/Technologie/Devoirs/devoir-de-synth%C3%A8se-n%C2%B02/devoir-de-synth%C3%A8se-n%C2%B02--2009-2010(r%C3%A9gion-kairouan).pdf