Anderson, J. 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. PSAS 1872, 9, 292.