ulink doesn't show as footnote when using XSL-NS Stylesheets

<?xml version="1.0" encoding="UTF-8"?>
<book xmlns="http://docbook.org/ns/docbook"
	 xmlns:xl="http://www.w3.org/1999/xlink"
	 version="5.0" xml:lang="en">
    <title>Book Title</title>
    <chapter xml:id="c1">
        <title>Chapter Title</title>
        <section xml:id="s1">
            <title>Section Title</title>
			<para>
				Information on the XSL stylesheets used to translate DocBook source files into different output an be found in the book, 
				<citetitle>DocBook XSL: The Complete Guide</citetitle> by Bob Stayton. The book is also available 
				<link xl:href="http://sagehill.net/docbookxsl/index.html">online</link>.
			</para>
        </section>
    </chapter>
</book>