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