Leonard, Wolfgang
Frederick A. Praeger, 1962
Buku Teks SO
Fischer, George, author
Harvard University Press, 1952
Buku Teks
Kennan, George F., 1904-, author
An Atlantic Monthly Press Book, 1961
Buku Teks
Daniels, Robert V
Westview Press, 1988
Buku Teks
Lewin, Mostie
University of California Press , 1988
Buku Teks