Wherry, Frederick F., author
Polity Press, 2012
Buku Teks
Dorfman, Robert, author
Prentice-Hall, 1967, c.1972
Buku Teks
DeRosa, Thomas F., author
John Wiley & Sons, 2009
Buku Teks
Schmookler, Jacob
Harvard University Press, 1972
Buku Teks
Morton, Rogers C. B.
U.S. Department of Commerce, 1975
Buku Teks