1. Gabriel(1963 ), "Principles and Practice of Rectal Surgery ", fifth edition , H. K. Lewis & Co. Ltd, London: 299 .
2. J. C. Goligher(1967 , reprinted1967 ), "Surgery of the Anus, Rectum and Colon ", second edition , Bailliere, Tindall and Cassell, London: 218 .Idem, ibidem: 218 .
3. Carcinoma Associated With Fistula-in-Ano