9Mushak P.Daris JM.Crocetti AF,et a1.Prenatal and postnatal effects of low level lead exposure,Intergrated summary of a report to U.S congress on childhood lead poisoning Environ.Res,1989,50:11.
10Christine A.Swanson CA,King JC et al Zinc and Pregnancy Outcome.Am J,Clin Nutrition,1987,46:783.