Vickrey, William
Ronald Press, 1947
Buku Teks SO
edited by Karen Lamb
Penguin Books, 1990
Buku Teks SO
Williamson, J. Peter (John Peter)
Scott, Foresman, 1968
Buku Teks SO
White, Patrick, 1912-1990
Jonathan Cape, 1988
Buku Teks SO
Nightingale, Kath
Prentice-Hall, 2002
Buku Teks