SMITH, Beverley. Isbister, an Orkney Islands Council Guardianship Monument. Proceedings of the Society of Antiquaries of Scotland, [S. l.], v. 119, p. 55–58, 1990. DOI: 10.9750/PSAS.119.55.58. Disponível em: https://journals.socantscot.org/index.php/psas/article/view/9350. Acesso em: 26 apr. 2024.