To refer to a location on a Web page outside the current
document, use the ulink element with a
url attribute that specifies the URL
(Uniform Resource Locator) of the target.
In the HTML output, this will produce a clickable link.
In the PDF output, DocBook will place the URL in a footnote.
Example:
See the <ulink url="http://www.nmt.edu/tcc/help/">TCC Help System</ulink>.
would display as: “See the TCC Help system.”