Caravan, Jill
Todtri Production Limited, 1996
Buku Referensi
Friedman, Lawrence M., 1930-
W.W. Norton, 1984
Buku Teks
Ketchum, Richard M.
American Heritage Publishing, 1960
Buku Teks
Musser, Charles
Macmillan Library reference USA,, 1990
Buku Referensi
Corner, James
Yale University Press, 1996
Buku Teks