Joass, J. (1871) “Note on the Discovery of Urns set in a Round Hole in the Ground under a Tumulus, and of an Inverted Urn covering Calcined Bones at Gordonbush, Sutherlandshire. In a Letter to John Stuart, LL.D., Secretary”, Proceedings of the Society of Antiquaries of Scotland, 8, p. 466. doi: 10.9750/PSAS.008.466.