1. Guidelines for the management of colorectal cancer document (2001) Association of Coloproctologists of Great Britain and Ireland (ACPGBI), p 28 http://www.acpgbi.org.uk/downloaddocs.html
2. Stranding S (ed) (2004) Gray’s anatomy: the anatomical basis of clinical practice, 39th edn. Elsevier Churchill Livingstone, New York, p 1199