Taher, Md Abu, et al. “Doppler Flow Velocity Indices (RI, PI, S D & PSV) of Fetal Middle Cerebral Artery in Normal Pregnancies: Correlation With Gestational Age of 20 to 40 Weeks”. BIRDEM Medical Journal, vol. 2, no. 2, Oct. 2012, pp. 77-80, doi:10.3329/birdem.v2i2.12306.