Elliott, David
Routledge, 1997
Buku Teks SO
Coley, David
John Wiley & Sons, 2008
Buku Teks
edited by Bob Everett, Godfrey Boyle, Stephen Peake and Janet Ramage
Oxford University Press, 2012
Buku Teks SO
Outhwaite, William
Blackwell, 2006
Buku Teks SO
Birkhauser GmbH, 2008
Buku Referensi