L. Pistorius, C. A. Cluver, I. Bhorat, and L. Geerts, “Trisomy 21 screening with αlpha software and the Fetal Medicine Foundation algorithm”, S Afr Med J, vol. 113, no. 11, pp. 27–34, Nov. 2023, doi: 10.7196/SAMJ.2023.v113i11.885.