There are two types of footnotes (or endnotes) in historical writing. Anthony Brundage in Going to the Sources calls them reference footnotes and content footnotes.¹
- Reference footnotes cite the bibliographic source of a quotation, fact or idea. The first footnote on this page is an example of a reference footnote.
- Content footnotes can be extended commentary, an exploration of a tangent of thought related to the subject in the main body of text, or a discussion of the historiography surrounding a topic. Here is one example of a content footnote displaying a 'conversation' about a source.

From: Lewis, Michael. Rioters and Citizens: Mass Protest in Imperial Japan. Berkeley: University of California Press, 1990.