LAMB, R G. The Cathedral of Christchurch and the monastery of Birsay. Proceedings of the Society of Antiquaries of Scotland, [S. l.], v. 105, p. 200–205, 1975. DOI: 10.9750/PSAS.105.200.205. Disponível em: https://journals.socantscot.org/index.php/psas/article/view/8882. Acesso em: 5 may. 2024.