Columbia subject headings:
Harvard subject headings:
Germany--Ethnic relations.
Immigrants--Germany--Societies, etc.--History.
Polish people--Germany--History.
Polish people--Germany--Societies, etc.--History.
Princeton subject headings:
Germany--Ethnic relations.
Immigrants--Germany--Societies, etc.--History.
Polish people--Germany--History.
Polish people--Germany--Societies, etc.--History.