Shumaila Yasin, Sarfraz Ahmed, Mariya Shahbaz, Sabeena Umer, Shazia Roman, Faiza Irshad, “Trisomy 21 Testing in Second Trimester: Reliability Comparison of Triple and Quadruple Testing in Pakistan”, Pakistan Journal of Medical & Health Sciences, vol. 17, no. 03, p. 492, Apr. 2023.