⁴Harbison, Peter. Guide to the National and Historic Monuments of Ireland. Dublin: Gill and Macmillan, 1992. 185.
In a later publication Harbison concludes, "it is now widely accepted that it probably belongs to the early centuries of Christianity in Ireland." (Harbison, Peter. "An Architectural Enigma." Irish Arts Review 23.3 (2006): 100-01.)