⁶Petrie, George, and D.J.S. O'Malley. "Aspects of George Petrie. V. An Essay on Military Architecture in Ireland Previous to the English Invasion." Proceedings of the Royal Irish Academy. Section C: Archaeology, Celtic Studies, History, Linguistics, Literature 72 (1972): 236. [Read, 28 April, 1834 Published,18 December, 1972.]