Install sgml-base-doc by entering the following commands in the terminal:
sudo apt update sudo apt install sgml-base-doc
Description:
Documentation for sgml-base
This package contains the documentation for sgml-base, providing the SGML infrastructure directories and catalog file support, in HTML, PDF and plain text format.
Homepage: http://debian-xml-sgml.alioth.debian.org
Version: 1.99.2
Section: universe/doc