Smith, J. A. (1880) “Additional Notes to Notice of the Remains of the Great Auk (Alca impennis, Linn.), found in Caithness; with Notes of its Occurrence, &c., in Scotland, and of its Early History”, Proceedings of the Society of Antiquaries of Scotland, 14, pp. 436–444. doi: 10.9750/PSAS.014.436.444.