DOCBOOK: URLs in bibliography

Hi all

I want to add some URLs to my book bibliography. I've tried the
following:

<biblioentry>
  <bibliomisc>
    <ulink url="http://www.qsl.net/lu8ual/ssoo1.html"/>
  </bibliomisc>
  <title>Sistemas Operativos - Un poco de historia</title>
</biblioentry>

but does not work (I only see the title). I want both things in the
printed version.

Well, what really matters to me is how should I write the biblioentry...
I can't find the right way.

Thanks!

-- 
La ignorancia es la felicidad.

Julio Merino <> ICQ: 18961975