Citations are important in Wikipedia to ensure that information comes from actual, reliable sources (WP:V, WP:CITE). There are two preferred ways of doing so: footnotes and parenthetical/Harvard citations. Citations can also be placed as external links, but these are not preferred because they are prone to link rot and usually lack the full information necessary to find the original source in cases of link rot. In cases where citations are lacking, the template {{fact}} can be added after the statement in question.