This index records published entries in the Encyclopedia in chronological order, and their versions archived in WebCite and published in the journal Knowledge organization, section “Review of concepts in KO”. For each IEKO article, one or more different versions may be published and saved at the IEKO website (cfr. its colophon). All versions may not be archived in WebCite. WebCite has been down during a period in Summer 2019. Now it is up again, but displays the following message: "We are currently not accepting archiving requests. The archival state/snapshots of websites that have been archived with WebCite in the past can still be accessed and cited." The articles in IEKO are also covered by the Internet Archive where some versions can be found by the Wayback Machine.