Office for National Statistics, Index of Place Names in Great Britain (IPN) 2016 : User Guide, , 40 p. (lire en ligne [PDF]), p. 6 et 16.
gazetteer.org.uk
The Association of British Counties, 4. Notes for Historians and Genealogists, Gazetteer of British Place Names (présentation en ligne).
The Association of British Counties, Appendix B. Places in England and Wales affected by the Counties (Detached Parts) Acts 1844, Gazetteer of British Place Names (présentation en ligne).
walesonline.co.uk
« A New History of Wales: Professor Chris Williams asks why Monmouthshire belongs to Wales », Wales Online, (lire en ligne).