Study Search Results Your query returned 1 results. Series results are grouped under the most relevant study. You can ungroup series results. Use the search box below to revise your search, or start a new search. 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. Effects of Preferred Provider Organizations on Health Care Use and Costs: Pooled Cross-Sectional Time Series, First Quarter 1988 Through First Quarter 1990 (ICPSR 6373) Smith, Dean G.