Columbia subject headings:
Border patrols--United States.
National security--United States.
Terrorism--United States--Prevention.
United States. Dept. of Homeland Security.
Harvard subject headings:
Border patrols--United States
National security--United States
Terrorism--United States--Prevention
United States. Department of Homeland Security.
Princeton subject headings:
Border patrols--United States.
National security--United States.
Terrorism--United States--Prevention.
United States. Department of Homeland Security