Columbia subject headings:
Emigration and immigration--Research--Congresses.
Harvard subject headings:
Emigration and immigration--Research--Congresses.
Emigration and immigration--Statistics--Congresses.
United States--Emigration and immigration--Congresses.
Princeton subject headings:
Emigration and immigration--Research--Congresses.
Emigration and immigration--Statistics--Congresses.
United States--Emigration and immigration--Congresses.