Among the Mortimers' vast estates, Trim was the family seat through the early fifteenth century.
David Beresford, "Mortimer, Roger," in Dictionary of Irish Biography.
R.R. Davies, "Mortimer, Roger, fourth earl of March and sixth earl of Ulster" in Oxford Dictionary of National Biography.
P. David Sweetman, G.F. Mitchell, R.J. Mansfield, and M. Dolley, "Archaeological Excavations at Trim Castle, Co. Meath, 1971-74," Proceedings of the Royal Irish Academy 78 (1978): 127-198.
Margaret K. Smith