Columbia subject headings:
Germany--Economic conditions--Congresses.
Germany--Emigration and immigration--Economic aspects--Congresses.
Harvard subject headings:
Foreign workers--Germany--Congresses.
Germany--Economic conditions--20th century--Congresses.
Germany--Emigration and immigration--Congresses.
Princeton subject headings:
Germany--Economic conditions--Congresses.
Germany--Emigration and immigration--Economic aspects--Congresses.