Perhaps you should try some spelling variations:
actors research » factors research, actions research, author's research
option research » opinion research, action research, optics research
multi actors » multi actor, multi acteurs, multi factor
multi option » multi location, multi population, multi ratios
july 2007 » july 2008, july 2012, 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 actors research : july 2013 ) or ( multi option research : july 2007 ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( multi actors research : july 2013 ) OR ( multi option research : july 2007 )).
• Adding a wildcard symbol may retrieve word variants: (( multi actors research : july 2013 ) or ( multi option research : july 2007 ))*.