Karl Marx is the author of Karl Marx, Frederick Engels : Collected Works. Vol. 20 (1975), Karl Marx, Frederick Engels : Collected Works. Vol. 40 (1975), Karl Marx, Frederick Engels : Collected Works. Vol. 2 (1975), Karl Marx, Frederick Engels : Collected Works. Vol. 4 (1975), Karl Marx, Frederick Engels : Collected Works. Vol. 10 (1975).