Study Search Results Your query returned 3 results. Series results are grouped under the most relevant study. You can ungroup series results. Results per page: 25 50 100 Sort by: Title A-Z Released/Updated Time Period Most Cited in ICPSR Bib. Most Downloaded (?) Study Title/Investigator 1. Center for Research on Social Reality [Spain] Survey, May 1995: Old Age (ICPSR 6969) Centro de Investigaciones Sobre la Realidad Social (CIRES) 2. Danish 1905 Cohort Study, 1998 (ICPSR 3960) University of Southern Denmark. Institute of Public Health; Duke University 3. Longitudinal Study of Aging Danish Twins, 1995 (ICPSR 21041) Christensen, Kaare; Vaupel, James W.