Perhaps you should try some spelling variations:
"improving food performance series." » "improving food performance metrics.", "improving food performance reviews.", "improving food performance review.", "improving good performance series.", "improving poor performance series.", "improving fund performance series.", "improving land performance series."
"improving rural performance based." » "improving pupil performance based.", "improving thermal performance based.", "improving overall performance based.", "improving rural performance measures.", "improving urban performance based.", "improving social performance based."

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

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