1. Augustine of Hippo (St. Augustine). Confessions. 397 AD. Translated by Edward Bouverie Pusey. Book 12. New York: P. F. Collier and Son, 1909–1914. https://www.sacred-texts.com/chr/augconf/aug12.htm.
2. [Brewster, David]. Article IX: Rev. of Vestiges of Natural History of Creation. 3, no. 6 (August 1845): 470–516. https://go.openathens.net/redirector/liberty.edu?url=https://www.proquest.com/historical-periodicals/art-ix-vestiges-natural-history-creation/docview/4272981/se-2.
3. Browne, Janet. Charles Darwin: The Power of Place. London: Jonathan Cape, 2002.
4. Browne, Janet. Darwin’s Origin of Species: A Biography. New York: Atlantic Monthly Press, 2006.
5. Burkhardt, Frederick, ed. Charles Darwin’s Letters: A Selection, 1825–1859. Cambridge: Cambridge University Press, 1996.