Footnote reference:
Code:
<a class="ref" href="../Text/Notes4.xhtml#noteC4_3" id="refC4_3">3</a>
Footnote target:
Code:
<a class="ref" href="../Text/Chapter4.xhtml#refC4_3" id="noteC4_3">3</a>
But remember it's not just my syntax that's affected, since a couple of other epubs I've tested have also failed to be rendered properly in some readers.
Update: I've tested several more free readers in Android; some of them handle the internal links in my project, some don't. Among those that do are FB Reader and Mantano. The Asus MyLibrary reader does not.