Anderson, J. 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. PSAS 1880, 14, 445-452.