THURLBY, Malcolm. Aspects of the architectural history of Kirkwall Cathedral. Proceedings of the Society of Antiquaries of Scotland, [S. l.], v. 127, p. 855–888, 1998. DOI: 10.9750/PSAS.127.855.888. Disponível em: https://journals.socantscot.org/index.php/psas/article/view/9988. Acesso em: 5 may. 2024.