Adamson, Dr. I. (1995): . Bangor, Pretani Press. Third Impression. Bardon, J. (2001): . Belfast, Blackstaff Press. New Updated Edition. Canny, Nicholas (2003): , Oxford University Press, Oxford. Curtis, Edmund (2000): , Routledge, ISBN 0-415-27949-6 Moody T.W & Martin, F.X. (1984): , Mercier Press, 2. utg., ISBN 0-85342-715-1 O Siochru, Micheal (2008): , Faber & Faber, London.