Wikipedia:Citation Templates
Citation templates are used to format citations in a consistent way, as an alternative to formatting the citations by hand. The use of citation templates is neither encouraged nor discouraged. Templates may be used or removed at the discretion of individual editors, subject to agreement with other editors on the article. Because templates can be contentious, editors should not add citation templates, or change an article with a consistent citation format to another, without gaining consensus; see WP:CITECONSENSUS and WP:CITEVAR. The various citation templates below may be freely mixed, since they all produce a similar format.
Read more about Wikipedia:Citation Templates: Use in Footnotes, Using The Same Footnote Multiple Times, Using Multiple Pages From The Same Source, Creating Links To Citations, Using Commas Rather Than Periods, Examples, Harvard Reference and Shortened Footnote Examples, Variations