Wright, Chester
Massachusetts Addison-Wesley 1973,
Buku Teks
James, Clifford L.
Prentice-Hall, 1951
Buku Teks
Ekelund, Robert B. Jr
Little, Brown & Co., 1986
Buku Teks
Gwartney, James D.
Harcourt Brace Jovanovich, Publisher, 1987
Buku Teks
Roman, Daniel D.
Prentice-Hall, 1968
Buku Teks