This question already has an answer here:
I use letters to indicate footnotes, so I use the
\alph command to output the footnote number.
The problem is that
\alph can only handle numbers up to 26 (corresponding to the letter z). Is there any way to have the count continue with aa, ab, ac, ..., az, ba, bb, ... (or something similar) for the values 27, 28, 29, ...