Initiatives World Food Information System (页面存档备份,存于互联网档案馆) .World Food Programme Institutional Repository for InformationSharing (IRIS) (页面存档备份,存于互联网档案馆)
(原始内容存档 (PDF)于2017-11-11). Ritchie, D. M.; Thompson, K. The UNIX Time-Sharing System (PDF). Communications of the ACM. 1974, 17 (7): 365–375 [2020-03-09]