Perhaps you should try some spelling variations:
"improving rural performance reviews." » "improving rural performance review.", "improving rural performance reports.", "improving rural performance risks.", "improving pupil performance reviews.", "improving overall performance reviews.", "improving fiscal performance reviews.", "improving urban performance reviews.", "improving social performance reviews."
"improving thermal performance series." » "improving thermal performance metrics.", "improving thermal performance review.", "improving thermal performance targets.", "improving maternal performance series.", "improving human performance series.", "improving mental performance series."

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 reviews.") or ("improving thermal performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving rural performance reviews.") OR ("improving thermal performance series."))*.
• Removing quotes may allow a broader search: (( improving rural performance reviews. ) or ( improving thermal performance series. ))*.