Columbia subject headings:
Marx, Karl, 1818-1883.
Philosophy, German--19th century.
Proudhon, P.-J. (Pierre-Joseph), 1809-1865.
Harvard subject headings:
Marx, Karl, 1818-1883
Philosophy, German--19th century.
Philosophy, German.
Proudhon, P.-J. (Pierre-Joseph), 1809-1865.
Socialism--France--19th century.
Sociology--Philosophy
Princeton subject headings: