https://www.mathjax.org/
https://katex.org/
https://github.com/kostub/iosMath
https://github.com/gregcockroft/AndroidMath
https://shreevatsa.github.io/site/texdoc.net/texmf-dist/doc/generic/knuth/tex/tex.pdf
https://people.eecs.berkeley.edu/~fateman/temp/neuform.pdf (A Functional Description of TeXs Formula Layout)