Kaushal, L., A. Patil, and K. Kocherla. “Evaluation of Placental Thickness As a Sonological Indicator for Estimation of Gestational Age of Foetus in Normal Singleton Pregnancy”. International Journal of Research in Medical Sciences, vol. 3, no. 5, Jan. 2017, pp. 1213-8, https://www.msjonline.org/index.php/ijrms/article/view/1472.