Columbia subject headings:
Admission of nonimmigrants--Government policy--United States.
Aliens--Government policy--United States.
National security--United States.
Terrorists--United States--Identification.
Visas--United States.
Harvard subject headings:
Admission of nonimmigrants--Government policy--United States.
National security--United States
Noncitizens--Government policy--United States
Terrorists--United States--Identification.
Visas--United States.
Princeton subject headings:
Admission of nonimmigrants--Government policy--United States.
National security--United States.
Noncitizens--Government policy--United States.
Terrorists--United States--Identification.
Visas--United States.