Swan, Michael. Practical English usage: International Student's Edition. Oxford: Oxford University Press, 1996. Print.

The Oxford English Dictionary, ed James A.H. Murray and others,12 vols. (Oxford: At the Clarendon Press, 1884-1928; corrected reissue, 1933)

Webster's Third New International Dictionary, editor-in-chief, Philip Babcock Gove (Springfield: G. & C. Merriam Company, 1961)

Abrams, M.H., ed. The Norton Anthology of English Literature. New York: Norton, 1968.