Malik, Renuka, and Preeti Sharma. 2017. “Menstruating Umbilicus! A Rare Case Report of Primary Umbilical Endometriosis With Review of Literature”. International Journal of Reproduction, Contraception, Obstetrics and Gynecology 5 (7):2453-56. https://doi.org/10.18203/2320-1770.ijrcog20162149.