Langguth, A.J
Simon and Schuster, 1988
Buku Teks
edited by Edmund S. Morgan
Prentice-Hall, 1965
Buku Teks
Morris, Richard B., author
Van Nostrand Reinhold, 1955
Buku Teks
Unrau, Harlan D.
National Park Service, 1976
Buku Teks
Carrington, Selwyn H. H.
Foris Publications, 1988
Buku Teks