MARSHALL, Dorothy N. Carved stone balls. Proceedings of the Society of Antiquaries of Scotland, [S. l.], v. 108, p. 40–72, 1979. DOI: 10.9750/PSAS.108.40.72. Disponível em: https://journals.socantscot.org/index.php/psas/article/view/8959. Acesso em: 6 may. 2024.