Columbia subject headings:
Harvard subject headings:
Fortification, Roman--Benelux countries.
Fortification, Roman--France.
Fortification, Roman--Germany.
Fortification, Roman--Great Britain.
Princeton subject headings:
Fortification, Roman--Benelux countries.
Fortification, Roman--France.
Fortification, Roman--Germany (West).
Fortification, Roman--Great Britain.