«ZDNet Definition for: Closed Source». ZDNet. Arxivat de l'original el 2008-07-31. [Consulta: 7 maig 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. Arxivat de l'original el 2008-07-31. [Consulta: 7 maig 2011]. «Proprietary software owned by one organization. The term is typically used only in discussions that contrast open source software with proprietary software»