1. Allen, A. C.:In Anderson, W. A. D. (ed.): Pathology. Ed. 5, St. Louis, The C. V. Mosby Company, 1966, vol. 2, chapt. 40.
2. Bacon, H. E.: Cancer of the Colon, Rectum and Anal Canal. Philadelphia, J. B. Lippincott Company, 1964.
3. Bunstock, W. H.: Basal cell carcinoma of the anus. Am. J. Surg.95: 822, 1958.
4. Gabriel, W. B.: The Principles and Practice of Rectal Surgery. Ed. 5, London, H. K. Lewis and Co. Ltd., 1963.
5. Grinvalsky, H. T. and E. B. Helwig: Carcinoma of the anorectal junction. I. Histological considerations. Cancer.9: 480, 1956.