 https://github.com/Khan/KaTeX/blob/f71f469d4b3ca97654702a0807e736d176f4c4c5/src/macros.js#L711-L714 https://github.com/Khan/KaTeX/blob/f71f469d4b3ca97654702a0807e736d176f4c4c5/test/screenshotter/test.tex#L16-L22
