editorial information compiled by the Economist
The Economist Newspaper Limited, 1984
Buku Referensi
MacKay, R.A.
The Ryerson Press, 1935
Buku Teks
Routledge, 1992
Buku Teks
edited for the Society of American Historians by Courtlandt Canby & Nancy E. Gross
New American Library, 1954
Buku Teks SO
Revill, J.C.
Longman, 1959
Buku Teks SO