Chholak, D., P. Gupta, and S. Khajotia. “Study to Evaluate Association of Umbilical Coiling Index and Perinatal Outcome”. International Journal of Reproduction, Contraception, Obstetrics and Gynecology, vol. 6, no. 2, Jan. 2017, pp. 408-12, doi:10.18203/2320-1770.ijrcog20170025.