Columbia subject headings:
Harvard subject headings:
Belgium--Emigration and immigration--History--19th century.
Poland--Emigration and immigration--History--19th century.
Polish people--Belgium--History--19th century.
Princeton subject headings:
Belgium--Emigration and immigration--History--19th century.
Poland--Emigration and immigration--History--19th century.
Polish people--Belgium--History--19th century.