Source: http://bib.univ-oeb.dz:8080/jspui/bitstream/123456789/6931/1/-Memoire--%20Boussouf%20Raouf%20Amir%20-%20Master%20Ad-Syst%C3%A9me%20d%27Encadrement%20Collaboratif%20Assist%C3%A9%20par%20Ordinateur%20.pdf