Columbia subject headings:
Collective behavior--Congresses.
Crowding stress--Congresses.
Crowds--Congresses.
Mobs--Congresses.
Harvard subject headings:
Collective behavior--Congresses.
Crowding stress--Congresses.
Crowds--Congresses.
Mobs--Congresses.
Princeton subject headings:
Collective behavior--Congresses.
Crowding stress--Congresses.
Crowds--Congresses.
Mobs--Congresses.