SPENCER, D. B. Numismatic Typeforms of the Numerals Zero through Ten in Medieval Europe: A Classification System. KOINON: The International Journal of Classical Numismatic Studies, [S. l.], v. 4, p. 203–214, 2021. Disponível em: https://archaeopresspublishing.com/ojs/index.php/koinon/article/view/1117. Acesso em: 8 dec. 2023.