Source: http://www.utc.fr/~jollivet/GE21/Centre%20de%20Documentation%20GE21/RapportsMINEFI/Etude%20sur%20les%20nouveaux%20mod%E8les%20%E9conomiques%20du%20logiciel%20libre,%20MINEFI%20-%20logicielslibres.pdf