Perhaps you should try some spelling variations:
"aids vaccine research : july 2009" » "aids medicine research : july 2009", "aids vaccine research : july 2008", "aids vaccine research : july 2007", "aids vaccine research : july 2006", "aims vaccine research : july 2009", "aid vaccine research : july 2009"
"multi option research : july 2019" » "multi opinion research : july 2019", "multi action research : july 2019", "multi optics research : july 2019", "multi location research : july 2019", "multi population research : july 2019", "multi ratios research : july 2019", "multi option research : july 2013", "multi option research : july 2012", "multi option research : july 2015"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("aids vaccine research : july 2009") or ("multi option research : july 2019"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("aids vaccine research : july 2009") OR ("multi option research : july 2019")).
• Removing quotes may allow a broader search: (( aids vaccine research : july 2009 ) or ( multi option research : july 2019 )).
• Adding a wildcard symbol may retrieve word variants: (("aids vaccine research : july 2009") or ("multi option research : july 2019"))*.