Perhaps you should try some spelling variations:
"multi accident research : july 2009" » "multi action research : july 2009", "multi vaccine research : july 2009", "multi accident research : july 2013", "multi accident research : july 2012", "multi accident research : july 2011"
"multiple options research : july 2006" » "multiple imputations research : july 2006", "multi option research : july 2006", "multiple operations research : july 2006", "multiple action research : july 2006", "multiple opinion research : july 2006", "multiple options research : july 2013", "multiple options research : july 2012", "multiple options research : july 2011"

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("multi accident research : july 2009") or ("multiple options research : july 2006"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("multi accident research : july 2009") OR ("multiple options research : july 2006")).
• Removing quotes may allow a broader search: (( multi accident research : july 2009 ) or ( multiple options research : july 2006 )).
• Adding a wildcard symbol may retrieve word variants: (("multi accident research : july 2009") or ("multiple options research : july 2006"))*.