Fuentes, H. D., C. de J. C. Quijano, and C. R. Negrete. “Umbilical Endometriosis: A Case Report and Review of the Literature”. International Journal of Research in Medical Sciences, vol. 9, no. 5, Apr. 2021, pp. 1485-8, doi:10.18203/2320-6012.ijrms20211890.