Source: https://www.researchgate.net/profile/Denis_Tanguay/publication/32050008_Analyse_du_developpement_de_la_notion_de_preuve_dans_une_collection_du_secondaire/links/53da391c0cf2631430c802fd/Analyse-du-developpement-de-la-notion-de-preuve-dans-une-collection-du-secondaire.pdf