Noble, James. “Notice of a Stone, Apparently a Sinker, With Incised Figures of Animals, from a Tumulus at Bridge of Brogar, Stennis, Orkney”. Proceedings of the Society of Antiquaries of Scotland 22 (November 30, 1888): 266–267. Accessed November 24, 2024. https://journals.socantscot.org/index.php/psas/article/view/6263.