The University of Chicago Press,
Majalah, Jurnal, Buletin
Cowan, Douglas E.
BlackWell Publishing, 2007
Buku Teks SO
edited by Stewart Sutherland, Leslie Houlden, Peter Clarke, Friedhelm Hardy
Routledge, 1988
Buku Referensi
Ambalu, Shulamit
Dorling Kindersley, 2013
Buku Referensi
Burke, T. Patrick
Blackwell, 2005
Buku Teks SO