TALBOT, Eric. The Ring of Castlehill, Caithness - a Viking fortification?. Proceedings of the Society of Antiquaries of Scotland, [S. l.], v. 108, p. 378–379, 1979. DOI: 10.9750/PSAS.108.378.379. Disponível em: https://journals.socantscot.org/index.php/psas/article/view/8983. Acesso em: 3 may. 2024.