1. Anal canal;Fenger,1997
2. Gastrointestinal Pathology and Its Clinical Implications;Lewin,1992
3. The comparative anatomy and pathology of anal glands;McColl;Ann R Coll Surg Engl,1967
4. Endocrine cells in the anal canal;Fetissof;Virchows Arch A Pathol Anat Histopathol,1984
5. Melanocytes in the anal canal epithelium;Clemmenson;Histopathology,1991