Columbia subject headings:
Communism--History--19th century.
Engels, Friedrich, 1820-1895.
Working class--History--19th century.
Harvard subject headings:
Communism--History--19th century
Engels, Friedrich, 1820-1895
Labor movement--History--19th century.
Princeton subject headings:
Communism--History--19th century.
Engels, Friedrich, 1820-1895.
Labor movement--19th century.