The Absence of the Vomer in the First and Early Second Trimester of Pregnancy – A New Marker of Trisomy 21 and Trisomy 13 - Mihailovic, T.; Stimec, B. V.; Terzic, M.; Dmitrovic, A.; Micic, J. (Ultraschall in der Medizin - European Journal of Ultrasound, 2012)