GORDON, C A. Carving Technique on the Symbol Stones of North East Scotland. Proceedings of the Society of Antiquaries of Scotland, [S. l.], v. 88, p. 40–46, 1956. DOI: 10.9750/PSAS.088.40.46. Disponível em: https://journals.socantscot.org/index.php/psas/article/view/8457. Acesso em: 7 may. 2024.