Modelski, George
Free Press, 1972
Buku Teks SO
Masannat, George S., editor
Charles Scribner's Sons, 1970
Buku Teks
Edward, David V.
Holt, Rinehart and Winston, 1969
Buku Teks SO
Terry, George R.
Richard D. Irwin, 1958
Buku Teks SO
John Wiley & Sons, 1948
Buku Teks SO