Columbia subject headings:
Engels, Friedrich, 1820-1895--Bibliography.
Marx, Karl, 1818-1883--Bibliography.
Harvard subject headings:
Engels, Friedrich, 1820-1895--Bibliography.
Marx, Karl, 1818-1883--Bibliography.
Princeton subject headings:
Engels, Friedrich, 1820-1895--Bibliography.
Marx, Karl, 1818-1883--Bibliography.