Source: https://www.researchgate.net/profile/Paul-Claval/publication/272386899_Chronique_de_geographie_economique_XVI_La_theorie_des_droits_de_propriete/links/5709c7a108aea66081358ce7/Chronique-de-geographie-economique-XVI-La-theorie-des-droits-de-propriete.pdf