Dear kovidgoyal,
Viewer (2.9) doesn't popup the following footnote. It always works with Moon+ Reader, though. Do I need to turn on any setting?
Code:
<a href="#n1" epub:type="noteref"><span class="calibre4">[1]</span></a>
and
Code:
<aside id="n1" epub:type="footnote">
<p class="textnote">(1): tháng giêng</p>
</aside>