Kahn, Robert L., 1918-, author
John Wiley & Sons, 1981
Buku Teks
Golightley, Malcom, author
Learning matters Ltd., 2008
Buku Teks
Karban, Kate, author
UK Polity Press, 2011
Buku Teks
edited by Sarah Gehlert; Teri Arthur Browne
John Wiley & Sons, 2012
Buku Teks
Pheasant, Stephen, author
Macmillan, 1991
Buku Teks