Perhaps you should try some spelling variations:
"improving rural performance series." » "improving rural performance metrics.", "improving rural performance reviews.", "improving rural performance review.", "improving pupil performance series.", "improving thermal performance series.", "improving overall performance series.", "improving urban performance series.", "improving social performance series."
"improving human performance risk." » "improving loan performance risk.", "improving thermal performance risk.", "improving company performance risk.", "improving human performance size.", "improving human performance based.", "improving human performance _.", "improving urban performance risk."

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("improving rural performance series.") or ("improving human performance risk."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving rural performance series.") OR ("improving human performance risk.")).
• Removing quotes may allow a broader search: (( improving rural performance series. ) or ( improving human performance risk. )).
• Adding a wildcard symbol may retrieve word variants: (("improving rural performance series.") or ("improving human performance risk."))*.