Muir, R.J.; Fitches W.R.; Maltman A.J.; Bentley M.R. (1994). "Precambrian rocks of the southern Inner Hebrides—Malin Sea region: Colonsay, west Islay, Inishtrahull and Iona". In Harris A.L. & Gibbons W. (ed.). A Revised Correlation of Precambrian Rocks in the British Isles. Special Report. Vol. 22 (2 ed.). London: Geological Society. pp. 54–56. ISBN9781897799116. Retrieved 15 September 2012.