Perhaps you should try some spelling variations:
national research » educational research
vaccine research » medicine research
active vaccine » anti vaccine, positive vaccine
multi national » multinationals _
july 2012 » july 2013
july 2008 » july 2013, july 2020, 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: (( active vaccine research : july 2012 ) or ( multi national research : july 2008 ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( active vaccine research : july 2012 ) OR ( multi national research : july 2008 )).
• Adding a wildcard symbol may retrieve word variants: (( active vaccine research : july 2012 ) or ( multi national research : july 2008 ))*.