Install w3-dtd-mathml by entering the following commands in the terminal:
sudo apt update sudo apt install w3-dtd-mathml
Description:
Mathematical Markup Language V2.0 DTD
The Mathematical Markup Language (MathML) V2.0 is an XML application for describing mathematical notation and capturing both its structure and content. The docbook-mathml package allows you to generate output documents from source files that use MathML markup. . Includes a prototype extension of the XHTML 1.1 DTD that incorporates MathML 2.0.
Homepage: http://www.w3.org/TR/MathML2/
Version: 2.0.0.0-5
Section: universe/text