Perhaps you should try some spelling variations:
"multiple vaccines research : july 2012" » "multiple access research : july 2012", "multiple crises research : july 2012", "multiple faces research : july 2012", "multiple vaccine research : july 2012", "multiple practices research : july 2012", "multiple accidents research : july 2012", "multiple vaccines research : july 2013"
"multi past research : july 2007" » "multi art research : july 2007", "multi impact research : july 2007", "multi first research : july 2007", "multi party research : july 2007", "multi plant research : july 2007", "multi page research : july 2007", "multi past research : july 2008", "multi past research : july 2013", "multi past research : july 2020"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("multi past research : july 2007") or ("multiple vaccines research : july 2012"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("multi past research : july 2007") OR ("multiple vaccines research : july 2012")).
• Removing quotes may allow a broader search: (( multi past research : july 2007 ) or ( multiple vaccines research : july 2012 )).
• Adding a wildcard symbol may retrieve word variants: (("multi past research : july 2007") or ("multiple vaccines research : july 2012"))*.