ramsay, William
Macmillan, 1972
Buku Teks
Mills, Edwin S., author
W.W. Norton, 1978
Buku Teks
Kneese, Allen V., author
The Johns Hopkins Press , 1968
Buku Teks
Pearce, D. W. (David William), 1941-, author
Harvester Wheatsheaf, 1990
Buku Teks
American Enterprise Institute for Public Policy Research, 1973
Buku Teks