Perhaps you should try some spelling variations:
multiple imputations » multiple imputation
imputations research » operations research, population research, institutions research
option research » opinion research, action research, operations research
multi option » mali options, multiple options
july 2009 » july 2006, july 2012, july 2011

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 2009 ) or ( multi option research : july 2013 ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( multiple imputations research : july 2009 ) OR ( multi option research : july 2013 )).
• Adding a wildcard symbol may retrieve word variants: (( multiple imputations research : july 2009 ) or ( multi option research : july 2013 ))*.