Sometimes I want to put a subscript or superscript to the left of an argument. In LaTeX documents, I have used the `\prescript` command from the `mathtools` package, as described [here](https://tex.stackexchange.com/questions/109694/the-prescript-command-from-the-mathtools-package-gives-incorrect-alignment). But Mathjax does not recognize this command. Is there an alternative using more basic commands that might be supported by Mathjax?