CALLANDER, J Graham. Notes on the Roman Remains at Grassy Walls and Bertha, near Perth. Proceedings of the Society of Antiquaries of Scotland, [S. l.], v. 53, p. 137–152, 1919. DOI: 10.9750/PSAS.053.137.152. Disponível em: https://journals.socantscot.org/index.php/psas/article/view/7456. Acesso em: 29 apr. 2024.