6Wang YP, Miao L, Dai L, et al. Mortality rate for children under 5 years of age in China from 1996 to 2006. Public Health, 2011, 125:301-307.
7National Birth Defects Prevention Network (NBDPN). Guidelines for conducting birth defects surveillance//Sever LE, ed. Atlanta, GA: National Birth Defects Prevention Network, Inc., 2004.
8Wikipedia. List of countries by infant mortality rate. http://en. wikipedia.org/wiki/List_of_countries_by_infant_mortality_rate.
9Reynolds MA, Schieve LA, Martin JA, et al. Trends in multiple births conceived using assisted reproductive technology, United States, 1997-2000. Pediatrics, 2003,111 : 1159-1162.