Columbia subject headings:
Air raid shelters--Italy--History--Congresses.
Border security--Europe--History--Congresses.
Border security--Italy--History--Congresses.
Europe--History--1918-1945--Congresses.
Fortification--Europe--History--Congresses.
Fortification--Italy--History--Congresses.
Military architecture--Europe--History--Congresses.
Military architecture--Italy--History--Congresses.
Underground construction--Congresses.
Harvard subject headings:
Air raid shelters--Italy--History--Congresses.
Border security--Europe--History--Congresses.
Border security--Italy--History--Congresses.
Europe--History--1918-1945--Congresses.
Fortification--Europe--History--Congresses.
Fortification--Italy--History--Congresses.
Military architecture--Europe--History--Congresses.
Military architecture--Italy--History--Congresses.
Underground construction--Congresses
Princeton subject headings:
Air raid shelters--Italy--History--Congresses.
Border security--Europe--History--Congresses.
Border security--Italy--History--Congresses.
Europe--History--1918-1945--Congresses.
Fortification--Europe--History--Congresses.
Fortification--Italy--History--Congresses.
Military architecture--Europe--History--Congresses.
Military architecture--Italy--History--Congresses.
Underground construction--Congresses.