Billington, Michael O., author
EIR News Service, 2000
Buku Teks
Scott, Andrew M., author
Holt, Rinehart & Winston, 1959
Buku Teks
edited by Howard J. Wiarda, Harvey F. Kline
Westview Press, 2007
Buku Teks
Busey, James L., author
Random House, 1968
Buku Teks
Aranson, Peter H.
Winthrop Publishers, 1981
Buku Teks