Callander, J Graham. “Notes on (1) Certain Prehistoric Relics from Orkney, and (2) Skara Brae: Its Culture and Its Period”. Proceedings of the Society of Antiquaries of Scotland 65 (November 30, 1931): 78–114. Accessed November 21, 2024. https://journals.socantscot.org/index.php/psas/article/view/7811.