Perhaps you should try some spelling variations:
"multi vaccine research : july 2007" » "multi medicine research : july 2007", "anti vaccine research : july 2007", "multiple vaccines research : july 2007", "multi vaccine research : july 2008", "multi vaccine research : july 2013", "multi vaccine research : july 2012"
"call options research : july 2009" » "call actions research : july 2009", "call optics research : july 2009", "call operations research : july 2009", "call option research : july 2009", "real options research : july 2009", "call options research : july 2008", "call options research : july 2019", "call options research : july 2006"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("multi vaccine research : july 2007") or ("call options research : july 2009"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("multi vaccine research : july 2007") OR ("call options research : july 2009"))*.
• Removing quotes may allow a broader search: (( multi vaccine research : july 2007 ) or ( call options research : july 2009 ))*.