Flavin, Christopher, author
Worldwatch Institute, 1985
Buku Teks
Adelman, M.A., author
Johns Hopkins University Press, 1972
Buku Teks
Horsnell, Paul, author
Oxford University Press, 1993
Buku Teks
Willrich, Mason
The Free Press, 1975
Buku Teks
Simmons, Matthew R., author
John Wiley & Sons, 2005
Buku Teks