Columbia subject headings:
Harvard subject headings:
Boon, George C.--Bibliography.
Fortification, Roman--Congresses.
Fortification, Roman--Great Britain--Congresses.
Great Britain--History, Military--55 B.C.-449 A.D.--Congresses.
Romans--Great Britain--Congresses.
Rome--Army--History--Congresses.
Princeton subject headings:
Fortification, Roman--Congresses.
Fortification, Roman--Great Britain--Congresses.
Great Britain--History, Military--55 B.C.-449 A.D.--Congresses.
Rome--Army--History--Congresses.