Search Results Use the search box below to revise your search, or start a new search. Studies (2) Variables Publications Your query returned 2 studies. Series results are grouped under the most relevant study. Ungroup series results to view all results. Sort by: Title A-Z Released/Updated Time Period Most Cited in ICPSR Bib. 1. Danish 1905 Cohort Study, 1998 (ICPSR 3960) University of Southern Denmark. Institute of Public Health; Duke University 2. Longitudinal Study of Aging Danish Twins, 1995 (ICPSR 21041) Christensen, Kaare; Vaupel, James W.