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