Perhaps you should try some spelling variations:
"multi operations research : july 2007" » "mutation operations research : july 2007", "poultry operations research : july 2007", "runtime operations research : july 2007", "multi operations research : july 2008", "multi operations research : july 2013", "multi operations research : july 2012"
"_ multifactor research : july 2019" » "_ multifactor research : july 2013", "_ multifactor research : july 2012", "_ multifactor research : july 2015", "_ multifaceted research : july 2019"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("multi operations research : july 2007") or ("_ multifactor research : july 2019"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("multi operations research : july 2007") OR ("_ multifactor research : july 2019")).
• Removing quotes may allow a broader search: (( multi operations research : july 2007 ) or ( _ multifactor research : july 2019 )).
• Adding a wildcard symbol may retrieve word variants: (("multi operations research : july 2007") or ("_ multifactor research : july 2019"))*.