Columbia subject headings:
Engels, Friedrich, 1820-1895.
Labor unions and communism.
Labor unions.
Marx, Karl, 1818-1883.
Harvard subject headings:
Engels, Friedrich, 1820-1895--Views on trade-unions.
Labor unions and communism.
Marx, Karl, 1818-1883--Views on trade-unions.
Princeton subject headings:
Engels, Friedrich, 1820-1895--Views on trade-unions.
Labor unions and communism.
Marx, Karl, 1818-1883--Views on trade-unions.