The PreTeXt Guide

Footnotes are not too hard, just use <fn>, but note that for the time being, what can go inside a footnote is very, very restricted.¹ For instance, you can’t put a <p> (and thus you can’t put lists) inside a footnote. Also, no displayed math via <me>. There’s a lot of care being taken because of the prospect of footnotes inside footnotes inside footnotes.

Because of the restrictions on footnotes, it is important to keep them short. A good alternative for longer things that are somewhat digressional is the aside, which comes in three flavors: <aside>, <biographical>, <historical>. Each of these allows an optional title and then a variety of tags such as <p>, <figure>, and <sidebyside> (and many more).

<aside>
  <title>A Sample Aside</title>
  <p>
    Here is some text inside a sample aside.
    I'm going to put the Pythagorean identity below:
    <me>
      \sin^2(x) + \cos^2(x) = 1
    </me>.
  </p>

  <p>
    This aside has two paragraphs.
    You can't do that with a footnote.
  </p>
</aside>

The code in Listing 22.3.1 produces the aside “A Sample Aside”. A less contrived example of an aside can be found in Section 19.4.