Stevenson, J.H. 1926. Note on Three Metal Matrices of Seals (of apparently the thirteenth century or thereby) in the National Museum of Antiquities, which bear the Emblem of the Stag-head Cabossed. Proceedings of the Society of Antiquaries of Scotland. 60, (Nov. 1926), 218–226. DOI:https://doi.org/10.9750/PSAS.060.218.226.