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A footnote is for a reference that documents or elucidates the primary text.1 Footnotes are distracting; use them sparingly, if at all. Standard bibliographical references are better placed in a bibliography at the end of a document than in footnotes throughout.
[1] A footnote should complement or expand upon the primary text, but a reader should not need to read a footnote to understand the primary text. For a thorough discussion of footnotes, see The Chicago Manual of Style, which is published by the University of Chicago Press.