1. 1. RMH. McMinn, Last's Anatomy , 8th edn. Edinburgh: Churchill Livingstone, 1980 ; 401 -3 .
2. 2. PL Williams, R Warwick, M Dyson, and LH Bannister ) Gray's Anatomy , 37th edn. Edinburgh: Churchill Livingstone, 1989 ; 1370 -1 .
3. 3. WH. Hollinshead, Anatomy for Surgeons: Volume 2. The Thorax, Abdomen, and Pelvis . New York: Harper and Row, 1956 ; 708 -11 .
4. 4. GJ Romanes ) Cunningham's Textbook of Anatomy , 10th edn. London: Oxford University Press, 1964 ; 310 .
5. Anorectal musculature