1. Embryology, Anatomy and Diseases of the Umbilicus;Cullen,1916
2. Cases illustrative of obstetric disease. Case V;Storer;Boston med. surg. J.,1864
3. Demonstrations of Physical Signs in Clinical Surgery;Bailey,1960
4. Umbilical endometriosis: a benign cause of bleeding;Dunlap;Sth. med. J., Nashville,1955
5. Umbilical metastasis;Horn;Archs intern. Med.,1964