Columbia subject headings:
Poland--Emigration and immigration--History--20th century.
United States--Emigration and immigration--History--20th century.
Harvard subject headings:
Poland--Emigration and immigration--History--20th century.
United States--Emigration and immigration--History--20th century.
Princeton subject headings:
Poland--Emigration and immigration.
Polish Americans--History.
United States--Emigration and immigration.