Maternal serum screening for Down syndrome in the first trimester: experience from Belarus - Tsukerman, G L; Gusina, N B; Cuckle, H S (Prenat Diagn, 1999)
. Doi: 10.1002/(SICI)1097-0223(199906)19:6<499:AID-PD555>3.0.CO;2-6