Perhaps you should try some spelling variations:
multiple imputations » multiple imputation
imputations research » operations research, population research, institutions research
opinion research » action research
multi opinion » multi option
july 2012 » july 2013

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( multiple imputations research : july 2012 ) or ( multi opinion research : july 2012 ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( multiple imputations research : july 2012 ) OR ( multi opinion research : july 2012 )).
• Adding a wildcard symbol may retrieve word variants: (( multiple imputations research : july 2012 ) or ( multi opinion research : july 2012 ))*.