Benham, Frederic, author
Pitman Publishing Corporation, 1941
Buku Klasik
Wonderling, David, author
Open University Press, 2005
Buku Teks
by Pauline Mulholland ... [et al.]
Pitman, 1983
Buku Teks
Lipsey, Richard G., 1928-, author
Harper Collin, 1996
Buku Teks
Adreson, W. H. Locke, author
Prentice Hall of India, 1986
Buku Teks