Microtonal Composition by Thomas Nicholson and Marc Sabat, until just today, though it looks like it's been around since Sep. 2018: https://marsbat.space/pdfs/JI.pdf
I haven't had a chance to read through the whole thing yet, but I skimmed the notation section and it looks pretty great! HEJI being Sagittal's main competition aside...
![Smile :)](./images/smilies/icon_e_smile.gif)