1 Cecil G. Sheps Center for Health Services Research, University of North Carolina at Chapel Hill, Chapel Hill, NC; Schools of Social Work and Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC. Electronic address: [email protected].
2 Leiden University Medical Center, Department of Public Health and Primary Care, Leiden, The Netherlands; Radboud University Medical Center, Department of Primary and Community Care, Nijmegen, The Netherlands.