Anderson, Joseph. “Notice of the Excavation of the Brochs of Yarhouse, Brounaben, Old Stirkoke, Bowermadden, and Dunbeath, in Caithness; With Remarks on the Period of the Brochs; And an Appendix, Containing a List of Brochs in Scotland, and Early Notices of Many of Them”. Proceedings of the Society of Antiquaries of Scotland, vol. 9, Nov. 1872, p. 292, doi:10.9750/PSAS.009.292.