by edited by David F. Heathfield
Macmillan, 1976
Buku Teks SO
Allen, R.G.D.
Macmillan, 1973
Buku Teks SO
Parkin, Michael, 1939-
Prentice-Hall, c1992
Buku Referensi
Morley, Samuel A.
The Dryden Press, 1984
Buku Teks
Samuelson, Paul Anthony, 1915-2009
New York, 2005
Buku Teks