1
Hofstadter, Richard. 1944 (1992). Social Darwinism in American Thought. Boston: Beacon Press.

Jones, Alwyn K. 1990. Social Symbiosis: A Gaian Critique of Contemporary Social Theory. The Ecologist 20 (3): 108-113.


2
Young, Robert M. 1987. Herbert Spencer and 'inevitable' progress. History Today 37 (August): 18-22.


3
Jones, Alwyn K. 1990. Social Symbiosis: A Gaian Critique of Contemporary Social Theory. The Ecologist 20 (3): 108-113.