Perhaps you should try some spelling variations:
"multiple imputations research : july 2006" » "multiple imputation research : july 2006", "multiple implications research : july 2006", "multiple mutation research : july 2006", "multiple reputation research : july 2006", "multiple imputations research : july 2008", "multiple imputations research : july 2007", "multiple imputations research : july 2013"
"multi option research : july 2009" » "multi opinion research : july 2009", "multi action research : july 2009", "multi optics research : july 2009", "multi location research : july 2009", "multi population research : july 2009", "multi ratios research : july 2009", "multi option research : july 2008", "multi option research : july 2007", "multi option research : july 2019"

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (("multiple imputations research : july 2006") OR ("multi option research : july 2009"))~.
• Removing quotes may allow a broader search: (( multiple imputations research : july 2006 ) or ( multi option research : july 2009 ))~.
• Adding a wildcard symbol may retrieve word variants: (("multiple imputations research : july 2006") or ("multi option research : july 2009"))*.