There are several useful parts of DocBook that are not discussed in this Tutorial. These include Callouts, Indexes, Glossaries, and Reference Pages. If you need to use any of these features, you should consult the DocBook Reference and/or purchase a DocBook book.
Below are a list of resources that will help you acquire and get started with DocBook.
DocBook technical committee page at OASIS
DocBook - the Definitive Guide online book
Norman Walsh's DocBook Site
Jorge Godoy's DocBook HOWTO
Mark Galassi's DocBook Intro
FreeBSD Documentation Primer
DocBook Install mini-HOWTO - useful if you want to compile yourself your tools
Bob DuCharme's PSGML tips for emacs