Hearn, Michael Patrick. The Critical Heritage Edition of the Wizard of Oz. New York, Schocken, 1986.
Littlefield, Henry. “The Wizard of Oz: Parable on Populism.” American Quarterly. v. 16, 3, Spring 1964, 47–58.
“‘Oz’ Author Kept Intentions to Himself”. The New York Times Company. February 7, 1992
Rogers, Katharine M. L. Frank Baum, Creator of Oz: A Biography. New York, St. Martin’s Press, 2002.
Sale, Roger. Fairy Tales and After: From Snow White to E. B. White. Cambridge, MA, Harvard University Press, 1978.