[1] University of Pittsburgh School of Medicine,Center for Health Equity, Research, and Promotion
[2] VA Pittsburgh Health Care System,Center for Research on Health Care
[3] University of Pittsburgh,Department of Biostatistics, Graduate School of Public Health
[4] University of Pittsburgh,Department of Obstetrics & Gynecology
[5] University of Washington School of Medicine,Health Services Research and Development
[6] VA Puget Sound Health Care System,undefined