Genealogical Collections concerning families in Scotland 1750-1 by Walter Macfarlane (edited by James Toshach Clark, Keeper of the Advocates' Library, Scottish History Society, Edinburgh, 1900, vol.2, p.513 - 530): 'Earls of Dunbar and March from Dugdale Forden, the Chronicle of Melrose, the Chartularys of Melrose & Coldstream', &c.
Northumberland Families by W. Percy Hedley, Society of Antiquaries of Newcastle-upon-Tyne, 1968, vol.i, pps:235-241, where she is named as 'Derdere'.
Andrew McDonald, Gospatric, second earl of Lothian (d. 1166), Oxford Dictionary of National Biography, Oxford University Press, 2004 accessed 27 Sept 2017