Columbia subject headings:
Border patrols--United States.
International economic relations.
National security--United States.
Terrorism--United States--Prevention.
Harvard subject headings:
Border patrols--United States
International economic relations.
National security--United States
Terrorism--United States--Prevention
Princeton subject headings:
Border patrols--United States.
International economic relations.
National security--United States.
Terrorism--United States--Prevention.