Install docbook-xsl-ns by entering the following commands in the terminal:
sudo apt update sudo apt install docbook-xsl-ns
stylesheets for processing DocBook 5 XML to various output formats
These are modular XSL stylesheets for processing documents composed with DocBook 5 XML and its derivatives. Unlike in docbook-xsl the DocBook namespace prefix has been added to element names in pattern matches and expressions. However processing of DocBook 4 documents is also possible with these stylesheets. For a more detailed explanation read http://www.sagehill.net/docbookxsl/ProcesingDb5.html. . The stylesheets provide XSLT transformations for (X)HTML, WordML, HTML Help, JavaHelp, Man page (nroff), Website, Eclipse Platform Help file and XSL Formatting Object (XSL-FO) output. The latter can be further processed to a number of print formats using FOP or TeX-based tools. . The stylesheets are modular in the sense that you can extend and, to some extent, customize them. The documentation is included in a separate package.