16Westropp, Thomas J. “Slane in Bregia, County Meath: Its Friary and Hermitage.” The Journal of the Royal Society of Antiquaries of Ireland, Fifth Series, Vol. 31, No. 4, (Dec. 31, 1901): 421-24.
The author writes of the gateway, "...it was formerly roofed and had an outer arch now fallen, and a side staircase up its southern jamb."