Perhaps you should try some spelling variations:
"multiple operations research : july 2013" » "multiple generations research : july 2013", "multiple migrations research : july 2013", "multiple options research : july 2013"
"mali national research : july 2009" » "mali educational research : july 2009", "bali national research : july 2009", "malawi national research : july 2009", "multi national research : july 2009", "mali national research : july 2008", "mali national research : july 2007", "mali national research : july 2019"

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

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• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"mali national research : july 2009\") OR (\"multiple operations research : july 2013\"))".
• Removing quotes may allow a broader search: (( mali national research : july 2009 ) OR ( multiple operations research : july 2013 )).
• Adding a wildcard symbol may retrieve word variants: (("mali national research : july 2009") OR ("multiple operations research : july 2013"))*.