Armstrong, Marion V., , Western Maryland Interpretive Association, 2002. Dupuy, Trevor N., Johnson, Curt, and Bongard, David L., , Castle Books, 1992, 1st Ed., ISBN 0-7858-0437-4. Eicher, John H., og Eicher, David J., , Stanford University Press, 2001, ISBN 0-8047-3641-3. Morris, John D., , Kent State University Press, 2000, ISBN 0-87338-659-0. Warner, Ezra J., , Louisiana State University Press, 1964, ISBN 0-8071-0822-7.