Perhaps you should try some spelling variations:
"call options research : july 2011" » "call actions research : july 2011", "call optics research : july 2011", "call operations research : july 2011", "call option research : july 2011", "real options research : july 2011", "call options research : july 2013", "call options research : july 2015", "call options research : july 2019"
"scale options research : july 2012" » "scale actions research : july 2012", "scale optics research : july 2012", "scale operations research : july 2012", "share options research : july 2012", "care options research : july 2012", "case options research : july 2012", "scale options research : july 2013"

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• Adding a wildcard symbol may retrieve word variants: (("call options research : july 2011") OR ("scale options research : july 2012"))*.