Naming the output file

Hi,

Am a newbie to docbook, please accept apologies if I've missed something obvious
but I've trawled the web and looked at man pages etc without success.

How can I specify the filename for the (main) output document?

I'm using docbook that came with Fedora Core 3 distro:

$ rpm -qa | grep -i docbook
docbook-utils-pdf-0.6.13-5
docbook-dtds-1.0-17.2
docbook-utils-0.6.13-5
docbook-style-xsl-1.61.2-2
docbook-style-dsssl-1.76-8

And transforming my xml source using the following command:

$ docbook2html user_guide.xml

The output I get is a file called book1.html and other supporting files.

I'd like to have that main file called user_guide.html

Would just rename it afterwards but it seems to be referenced in all the supporting files too.

I'm sure I'm missing something simple.

Thanks,
D.