Anderson, Joseph. 1872. “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 9 (November), 292.