1. Daniel, E. E., Tomita, T., Tsuchida, S. & Watanabe, M. Sphincters: Normal Function Changes in Disease (CRC Press, 1992).
2. Torgersen, J. The muscular build and movement of the stomach and duodenal bulb. Acta Radiol. Suppl. 45, 1–191 (1942).
3. Cai, W. Q. & Gabella, G. Structure and innervation of the musculature at the gastroduodenal junction of the guinea-pig. J. Anat. 139(Pt. 1), 93–104 (1984).
4. Goss, C.M. Anatomy of the Human Body by Henry Gray. 29th edn. (Lea & Febiger, 1973).
5. Hollinshead, W. H. Anatomy for Surgeons: The Thorax, Abdomen, and Pelvis 3rd edn, Vol. 2 (Harper & Row, 1982).