ALLEN, John Romilly. Notes on Celtic Ornament - The Key and Spiral Patterns. Proceedings of the Society of Antiquaries of Scotland, [S. l.], v. 19, p. 253–308, 1885. DOI: 10.9750/PSAS.019.253.308. Disponível em: https://journals.socantscot.org/index.php/psas/article/view/6154. Acesso em: 2 may. 2024.