http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/9508
data 05/03/1991
http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/3580
data 02/06/2003
http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/34540
data 06/25/2013
http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/4210
data 06/28/2013
http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/34704
data 07/10/2013
http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/34277
data 07/31/2013
http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/25261
http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/34740
data 08/01/2013
http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/28161
data 08/05/2013
http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/34306
data 08/29/2013
http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/25942
data 08/30/2013
http://www.icpsr.umich.edu/icpsrweb/ICPSR/studies/34585
data 09/05/2013