Columbia subject headings:
Chemical industry--Security measures--United States.
Chemical plants--Protection--United States.
Chemical plants--Risk assessment--United States.
National security--United States.
Terrorism--United States--Prevention.
Harvard subject headings:
Chemical industry--Security measures--United States.
Chemical plants--Protection--United States.
Chemical plants--Risk assessment--United States.
National security--United States
Terrorism--United States--Prevention
Princeton subject headings:
Chemical industry--Security measures--United States.
Chemical plants--Protection--United States.
Chemical plants--Risk assessment--United States.
National security--United States.
Terrorism--United States--Prevention.