Fischer, George
Harvard University Press, 1952
Buku Teks SO
Kennan, George F., 1904-
An Atlantic Monthly Press Book, 1961
Buku Teks SO
Daniels, Robert V
Westview Press, 1988
Buku Teks SO
Westview Press, 1991
Buku Teks
Lewin, Mostie
University of California Press , 1988
Buku Teks SO