Adding an index to your document is easy; the DocBook XSL stylesheets automatically cross-reference your tagged index words to generate the page numbers in the index section. For example, in the source XML of this document you'll see that the index section at the end is indicated by just “<index />”. Examples of how to mark up index entries in the document are in this paragraph (the section called “tips.xml”) and throughout the section called “tools.xml”. The key tag is indexterm.