[lrui]

This is my approach, it works in my NST.

<p>(honeycomb-structure)<sup><a class="Hyperlink" href="#id04a" id="id04">[4]</a></sup></p>

  <hr />
  <p class="FootnoteText"><a class="Hyperlink" href="#id04" id="id04a">[4]</a>　Vivienne Shue,The Reach of the state:sketches of the&nbsp;Chinese body politic,Stanford University Press,1998.</p>

CSS

Spoiler:

.FootnoteText {

border-bottom: 0;
border-top: 0;
display: block;
font-family: "微软雅黑", "ht", sans-serif;
font-size: 0.85em;
layout-grid-mode: char;
line-height: 130%;
margin-bottom: 0.5em;
margin-left: 1%;
margin-right: 1%;
margin-top: 0.5em;
padding-bottom: 0;
padding-top: 0;
text-indent: 2em;
}
.Hyperlink {
color: red;
cursor: pointer;
text-decoration: underline;
font-family: "宋体", "zw", sans-serif;
}

here is the sample.untitled sample.epub

if you use iBooks, you can try this way , it supports pop-up footnotes and only supports by EPUB 3.0 readers.
http://www.pigsgourdsandwikis.com/20...pub-3-and.html