cdnjs is a free distributed JS library delivery service.
Express is a web application framework for Node.js, released as free and open-source software under the MIT License. It is designed for building web applications and APIs.
MathJax is a cross-browser JavaScript library that displays mathematical notation in web browsers, using MathML, LaTeX and ASCIIMathML markup.
Progressive Web Apps (PWAs) are web apps built and enhanced with modern APIs to deliver enhanced capabilities, reliability, and installability while reaching anyone, anywhere, on any device, all with a single codebase.