Source: https://flsh.uit.ac.ma/images/cours%20en%20ligne/Sociologie/S1/1%20%C2%A0%D9%85%D9%8A%D8%A7%D8%AF%D9%8A%D9%86%20%D8%B9%D9%84%D9%85%20%D8%A7%D9%84%D8%A7%D8%AC%D8%AA%D9%85%D8%A7%D8%B9.pdf