1. Department of Sociology, Temple University, 713 Gladfelter Hall, 1115 West Polett Walk, Philadelphia, PA 19122, USA
2. Cancer Prevention and Population Sciences, Roswell Park Cancer Institute, Elm and Carlton Streets, Buffalo, NY 14263, USA
3. Division of Behavioral and Social Research, National Institute on Aging/National Institutes of Health, Gateway Building, Suite 3S600, 7201 Wisconsin Avenue, MSC 9205, Bethesda, MD 20892-9205, USA