Columbia subject headings:
Border patrols--United States.
Illegal aliens--Government policy--United States.
International economic relations.
National security--Economic aspects--United States.
Harvard subject headings:
Border security--United States
Illegal immigration--Government policy--United States.
International economic relations
National security--Economic aspects--United States.
Noncitizens--Government policy--United States
Princeton subject headings:
Border patrols--United States.
Illegal aliens--Government policy--United States.
International economic relations.
National security--Economic aspects--United States.