Hartz, Louis
. 1955. The Liberal Tradition in America: An Interpretation of American Political Thought Since the Revolution. New York: Harcourt, Brace and World.
2.
Perlman, Selig
. 1928. The Theory of the Labor Movement. New York: Augustus M. Kelley.
3.
Sombart, Werner
. 1976. W7Ky is There No Socialism in the United States?White Plains, NY: International Arts and Sciences Press.