Perhaps you should try some spelling variations:
"port operations research : july 2009" » "market operations research : july 2009", "transport operations research : july 2009", "port operations research : july 2008", "port operations research : july 2007", "port operations research : july 2019"
"group operations research : july 2009" » "group operations research : july 2008", "group operations research : july 2007", "group operations research : july 2019"

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: (("port operations research : july 2009") OR ("group operations research : july 2009"))~.
• Removing quotes may allow a broader search: (( port operations research : july 2009 ) or ( group operations research : july 2009 ))~.
• Adding a wildcard symbol may retrieve word variants: (("port operations research : july 2009") or ("group operations research : july 2009"))*.