Anderson, Joseph. “Notice of a Fragment of a Silver Penannular Brooch, Ornamented With Gold Filigree Work and Amber Settings, Found at Achavrole, Dunbeath, Caithness, in 1860: And of Two Silver Brooches, the Property of Andrew Heiton, F.S.A. Scot., Said to Have Been Found in the Neighbourhood of Perth”. Proceedings of the Society of Antiquaries of Scotland, vol. 14, Nov. 1880, pp. 445-52, doi:10.9750/PSAS.014.445.452.