One might think that footnotes are obvious, but they did not really come into vogue until the 19th century. (Even today, citation is restricted to works that are meant to be "scholarly" in some degree or another. Most news journalism, for example, does not cite anything, and many popular histories today do not cite anything.)

While Leopold von Ranke did not invent footnotes, he popularized, and, Tony Grafton argues, "dramaticized," their use in a way that they became part of how serious historians proved they were doing serious history. This is one of the reasons Ranke is called "the father of history," and, again, this is more about how later period said "let's emulate him!" rather than him actually inventing anything (history — and footnotes — existed long before Ranke).

"[Ranke] dramatized the process of research and criticism, making the footnote and the critical appendix a source of pleasure rather than an occasion for apology. ... Ranke, however, made research and criticism glamorous and dramatic the sort of thing that attracted young men to working in seminars, writing dissertations, and joining the profession which was taking shape. One's footnotes really could now make one more famous than one's text. No wonder that so many bright young men chose problems of source criticism as the subjects for their well-annotated doctoral dissertations: content and form matched one another at last." — Anthony Grafton, "The Footnote from De Thou to Ranke," History and Theory 33, no. 4, (December 1994), 53-76, on 76.

I know little about the people you've mentioned in particular but one (Martin) is decidedly older than Ranke.