JOSS Paper equations are missing some definitions

[RainierBarrett]

Hello! I've been tapped as a reviewer for your recent submission to JOSS!
I've noticed that the PDF proof linked at the JOSS review issue thread doesn't contain definitions of all the symbols in the equations at the top of page 2:

I think the paper should include definitions of all the symbols used in these equations, as you have in your docs. That is, it's not clear what $f_c$, $f_s$, or $f_n$ are in the paper alone.