Twitter added support for "@replies" beginning in May 2008,[3] with any combination of @ with a username being turned into a hyperlink to the profile. On March 30, 2009, Twitter updated the feature and renamed it "Mentions" (i.e., to "mention" user "@janedoe") so as to include non-reply posts directed at individual users.[4]
R. Agrawal, J. Gehrke, D. Gunopulos, und P. Raghavan. SIGMOD '98: Proceedings of the 1998 ACM SIGMOD International Conference on Management of Data, Seite 94-105. ACM Press, (1998)