Source: http://www.ac-clermont.fr/fileadmin/user_upload/Actions_Educative/numerique-educatif/pedagogie/TRAAM/CoSciences/2016-2017/Formation_IFD_Co-sciences/Le_Puy-en-Velay/Travaux/Seance_1/Ecole_la_fontaine/fiche_seance_1_Vals.pdf