William Graham Sumner on Social Darwinism (ca.1880s) | The American Yawp Reader [online]. [cit. 2021-11-23]. Dostupné online. (anglicky)
archive.org
SUMNER, William. The Challenge of Facts and Other Essays. edited by Albert Galloway Keller. vyd. New Haven: Yale University Press, 1914. Dostupné online.
asanet.org
William G. Sumner. American Sociological Association [online]. 2009-06-04 [cit. 2021-11-23]. Dostupné online. (anglicky)