footnote-style-alist

footnote-style-alist is a variable defined in `footnote.el'.
Its value is

((numeric Footnote-numeric "[0-9]+")
 (english-lower Footnote-english-lower "[a-z]+")
 (english-upper Footnote-english-upper "[A-Z]+")
 (roman-lower Footnote-roman-lower "[ivxlcdm]+")
 (roman-upper Footnote-roman-upper "[IVXLCDM]+")
 (latin Footnote-latin "[¹²³ºª§¶]")
 (unicode Footnote-unicode "[⁰¹²³⁴⁵⁶⁷⁸⁹]+"))

Documentation:
Styles of footnote tags available.
By default only boring Arabic numbers, English letters and Roman Numerals
are available.
See footnote-han.el, footnote-greek.el and footnote-hebrew.el for more
exciting styles.