Anderson, Joseph. “Notice of the Excavation of the Brochs of Yarhouse, Brounaben, Bowermadden, Old Stirkoke, and Dunbeath, in Caithness, With Remarks on the Period of the Brochs; and an Aplpendix, Containing a Collected List of the Brochs of Scotland, and Early Notices of Many of them.And an Appendix Containing a Collected List of the Brochs of Scotland, and Early Notices of Many of Them”. Archaeologia Scotica, vol. 5, Nov. 1891, pp. 131-98, https://journals.socantscot.org/index.php/arch-scot/article/view/315.