1. Multiple pregnancy (first of two parts);Benirschke;N Engl J Med,1973
2. Multiple pregnancy: epidemiology, gestation, & perinatal outcome;Blickstein,2005
3. Smith's recognizable patterns of human malformation;Jones,2006
4. Pathology of the human placenta;Benirschke,2006
5. Sonographic determination of chorion type in twin gestation;Barss;Am J Obstet Gynecol,1985