Columbia subject headings:
Border patrols--United States.
Illegal immigration--Identification--Technological innovations--United States.
Noncitizens--Identification--Technological innovations--United States.
United States--Emigration and immigration.
United States. Immigration and Naturalization Service.
Harvard subject headings:
Border patrols--United States
Illegal immigration--Technological innovations--United States.
Noncitizens--Identification--Technological innovations--United States.
United States--Emigration and immigration
United States. Immigration and Naturalization Service
Princeton subject headings:
Border patrols--United States.
Illegal aliens--Identification--Technological innovations--United States.
United States--Emigration and immigration.
United States. Immigration and Naturalization Service