«ZDNet Definition for: Closed Source». ZDNet. Archivado desde el original el 31 de julio de 2008. Consultado el 20 de enero de 2011. «Proprietary software owned by one organization. The term is typically used only in discussions that contrast open source software with proprietary software».
«ZDNet Definition for: Closed Source». ZDNet. Archivado desde el original el 31 de julio de 2008. Consultado el 20 de enero de 2011. «Proprietary software owned by one organization. The term is typically used only in discussions that contrast open source software with proprietary software».