Joseph Bain, ed., Calendar of Documents Relating to Scotland, vol. II AD 1272-1307, p. 15 [1]
The so-called Chronicon Cumbriæ or Distributio Cumberlandiæ ad Conquestum Angliæ, surviving in several error-prone copies with many differences, published by: J. E. Prescott, ed., The register of the Priory of Wetherhal, p. 386 [2]; James Wilson, ed., The Register of the Priory of St. Bees, p. 493 [3]; and William Digdale, Monasticum Angliae, vol. 3, p. 584 [4].
doi.org
T. Graham, 'The Honour of Cockermouth', Transactions of the Cumberland and Westmorland Antiquarian and Archaeological Society, 2nd series, 29:69-79 doi:10.5284/1063285
electricscotland.com
Paul, James Balfour (1906). The Scots Peerage(PDF). Vol. 3. Edinburgh. p. 245.{{cite book}}: CS1 maint: location missing publisher (link)