1. Revisiting first-trimester fetal biometry.;Salomon;Ultrasound Obstet Gynecol,2003
2. Prenatal ages and stages-measures and errors.;O’Rahilly;Teratology,2000
3. description of age group XI, 13 to 20 somites, and age group XII, 21 to 29 somites.;Streeter;Contrib Embryol,1942
4. description of age group XIII, embryos about 4 or 5 millimeters long, and age group XIV, period of indentation of the lens vesicle.;Streeter;Contrib Embryol,1945
5. description of age groups XV, XVI, XVII, and XVIII.;Streeter;Contrib Embryol,1948