Perhaps you should try some spelling variations:
"doing national research : july 2009" » "doing educational research : july 2009", "going national research : july 2009", "using national research : july 2009", "among national research : july 2009", "doing national research : july 2008", "doing national research : july 2007", "doing national research : july 2019"
"call option research : july 2012" » "call opinion research : july 2012", "call action research : july 2012", "call optics research : july 2012", "call option research : july 2013", "all option research : july 2012", "hall option research : july 2012"

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: (("doing national research : july 2009") OR ("call option research : july 2012"))~.
• Removing quotes may allow a broader search: (( doing national research : july 2009 ) or ( call option research : july 2012 ))~.
• Adding a wildcard symbol may retrieve word variants: (("doing national research : july 2009") or ("call option research : july 2012"))*.