The America University, [date of publication not identified]
Buku Teks
Zinn, Howard, author
HarperCollins Publishers, 2005
Buku Teks
Walker, Edward Everett, 1900-1974, author
Charles Scribner's Sons, 1943
Buku Teks
Boyd, Anne Morris, author
H.W. Wilson, 1949
Buku Teks
edited by Roy A. Grisham, Jr., Paul D. McConaughy
WM. H. Wise, 1966
Buku Referensi