1. The role of prenatal care in preventing low birth weight;Alexander;The Future of Children,1995
2. American College of Obstetricians and Gynecologists, 1989. Standards for obstetric-gynecologic services. Am. Coll. Obstetr. Gynecol., Washington, DC.
3. Identification of causal effects using instrumental variables;Angrist;J. Am. Stat. Assoc.,1996
4. Problems with instrumental variables estimation when the correlation between the instruments and the endogenous explanatory variable is weak;Bound;JASA,1995
5. An evaluation of the impact of maternity care coordination on medicaid birth outcomes in North Carolina;Buescher;Am. J. Pub. Health,1991