Perhaps you should try some spelling variations:
options research » operations research, action research, opinion research
call options » call option, real options
june 2009 » june 2008, june 2013, june 2012
june 2014 » june 2013
july 2006 » july 2013, july 2012
july 2011 » july 2013, july 2012, june 2011

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

• If you are trying to use Boolean operators, they must be ALL CAPS: call options research : ((((june 2009) OR (june 2014))) OR (((july 2006) OR (july 2011))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "call options research : ((((june 2009) OR (june 2014))) or (((july 2006) or (july 2011))))~".
• Adding a wildcard symbol may retrieve word variants: call options research : ((((june 2009) OR (june 2014))) or (((july 2006) or (july 2011))))*.