Columbia subject headings:
Engels, Friedrich, 1820-1895.
Marx, Karl, 1818-1883.
Poland--History--19th century.
Harvard subject headings:
Engels, Friedrich, 1820-1895
Marx, Karl, 1818-1883
Poland--History--19th century
Princeton subject headings:
Engels, Friedrich, 1820-1895.
Marx, Karl, 1818-1883.
Poland--History--19th century.