edited by David Curtis Skaggs and Robert S. Browning III
Wadsworth, 1991
Buku Teks SO
edited by Frank Freidel and Norman Pollack
Rand McNally, 1963
Buku Teks SO
Herget, James E.
Texas: Rice University Press, 1990,
Buku Referensi
Graebner, Norman A.
McGraw-Hill, 1975
Buku Teks SO
Current, Richard N.
Alfred A. Knopf, 1965
Buku Teks SO