Columbia subject headings:
Europe--Emigration and immigration--Congresses.
Europe--Emigration and immigration--Government policy--Congresses.
Harvard subject headings:
Europe--Emigration and immigration--Congresses.
Europe--Emigration and immigration--Economic aspects--Congresses.
Europe--Emigration and immigration--Government policy--Congresses.
Princeton subject headings:
Europe--Emigration and immigration--Congresses.
Europe--Emigration and immigration--Economic aspects--Congresses.
Europe--Emigration and immigration--Government policy--Congresses.