Columbia subject headings:
Citizenship--Puerto Rico.
Citizenship--United States.
Puerto Ricans--United States.
United States--Emigration and immigration.
Harvard subject headings:
Citizenship--Puerto Rico.
Citizenship--United States
Puerto Ricans--United States
United States--Emigration and immigration.
Princeton subject headings:
Citizenship--Puerto Rico.
Citizenship--United States.
Puerto Ricans--United States.
United States--Emigration and immigration.