BTW, different apps/devices render footnotes differently. For example,
iBooks requires footnotes to be properly defined, while the
Kindle firmware (or KindleGen) uses heuristics and will usually display back-linked text as popup footnotes.
This works great for non-nested footnotes, however, if footnotes are nested, users usually can't tap links in footnote popup windows to display sub-footnotes.
I've created a simple epub3 test file with two different footnote sections.
The fist topic contains a link to non-nested footnote definitions:
while the second topic contains a link to nested footnote definitions:
(I used
<div> instead of
<aside> for backwards compatibility with epub2 readers.)
iBooks will display only the first footnote definition, if the definitions aren't nested. If they're nested, it'll display the footnote definition and all nested sub-footnote definitions, however tapping links in the popup window doesn't work. iBooks also seems to ignore styles in footnote popup windows.
eInk Kindles ignore nesting levels and will display only the first footnote definition. Users will need to tap Go To Footnotes to display sub-footnotes. However, if a sub-footnote link is tapped, its definition will be displayed in a popup window.