Wikipedia:WikiProject Aviation/Style guide/Citations

Citation styles
In general, articles may use one of two citation styles: The final choice of which style to follow is left to the discretion of an article's editors.
 * Footnotes
 * Footnotes are generally the more appropriate option when the level of citation is very dense, or where the citations include additional commentary. A number of different formatting styles are available; so long as an article is internally consistent, the choice of which to use is left to the discretion of the major editors.  For example, discursive notes may either be combined with citations (as here and here), or separated (as here).
 * A single footnote may be used to provide citations for any amount of material; while they typically apply to one or a few sentences, they may also cover entire paragraphs or sections of text. In cases where the connection between the citations and the material cited is not obvious, it is helpful to describe it explicitly (for example, "For the details of the operation, see Smith, First Book, 143–188, and Jones, Another Book, chapters 2–7; for the international reaction, see Thomas, Yet Another Book, 122–191").
 * Harvard-style references
 * Harvard-style references are useful where a limited number of simple citations is needed; they typically should not be used if the article has a significant number of other items in parentheses, or if citations must be accompanied by commentary.

Requesting citations
Editors should attempt to take a reasonable approach when requesting citations. Unless the accuracy of a statement is in significant doubt, it is generally better to start with a request for citations on the article's talk page, rather than by inserting fact tags—particularly large numbers of such tags—into the article. Over-tagging should be avoided; if a large portion of the article is uncited, adding an unreferenced or citation style tag to an entire section is usually more helpful than simply placing fact tags on every sentence. Note that some articles contain per-paragraph citations, so checking the citations at the end of a paragraph may yield information about facts or figures in the paragraph as a whole.