1. 1992. Spontaneous abortions: epidemiology. In: , , editors. Spontaneous abortion: diagnosis and treatment. London: Springer-Verlag; 1992. p 9-19.
2. Centers for Disease Control and Prevention. 1998. Metropolitan Atlanta Congenital Defects Program. Surveillance procedure manual and guide to computerized anomaly record. Atlanta, GA: Centers for Disease Control and Prevention.
3. Centers for Disease Control and Prevention. 2001. National Center for Health Statistics. Health United States, 2001, with urban and rural health chartbook. US Department of Health and Human Services publication no. (PHS) 01-1232, Aug 131-56.
4. Teratogen-Mediated Inhibition of Target Tissue Response to
Shh
Signaling
5. , , et al. 1997. Williams obstetrics. 20th ed. Stamford, CT: Appleton & Lange. p 839-844.