World Future Society, 1985.
Buku Teks
Published for the Latin American Studies Institute, by Louisiana State University Press, 1969
Buku Teks
Bowen, Howard R.
Rinehart & Company, 1948
Buku Teks
Basic Books, Inc., 1966
Buku Teks
John Wiley & Sons, 1978
Buku Teks