Renukesh, S. M., L. Rai, and S. Hebbar. “How Important Is Serum β-HCG in the Management of Ectopic Pregnancy?”. International Journal of Reproduction, Contraception, Obstetrics and Gynecology, vol. 4, no. 2, Feb. 2017, pp. 360-5, https://www.ijrcog.org/index.php/ijrcog/article/view/1881.