edited by Alexander Dalllin, Gail W. Lapidus
Westview press, 1991
Buku Teks SO
Lamont, Corliss
Philosophical Library, 1952
Buku Teks SO
Shacford, R.H.
Public Affairs Press, 1952
Buku Teks SO
Hough, Jerry F.
The Brookings Institution, 1980
Buku Teks SO
Frederick A, Praeger; George Allen and Unwin Ltd., 1964
Buku Teks SO