Perhaps you should try some spelling variations:
"multiple positions research : july 2007" » "multiple locations research : july 2007", "multiple options research : july 2007", "multiple solutions research : july 2007", "multiple transitions research : july 2007", "multiple positions research : july 2008", "multiple positions research : july 2013", "multiple positions research : july 2012"
"anti vaccine research : july 2007" » "anti medicine research : july 2007", "ant vaccine research : july 2007", "active vaccine research : july 2007", "aids vaccine research : july 2007", "anti vaccine research : july 2008", "anti vaccine research : july 2013", "anti vaccine research : july 2012"

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

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