Columbia subject headings:
Dikes (Engineering)--Great Britain.
England--Antiquities.
England--Boundaries--Wales.
Offa's Dyke (Wales and England)
Wales--Antiquities.
Wales--Boundaries--England.
Harvard subject headings:
Dikes (Engineering)--Great Britain.
England--Antiquities.
England--Boundaries--Wales.
Offa's Dyke (Wales and England)
Wales--Antiquities.
Wales--Boundaries--England.
Princeton subject headings:
Earthworks (Archaeology)--Great Britain.
England--Antiquities.
Offa's Dyke (Wales and England)
Offa, King of the Mercians, -796.
Wales--Antiquities.