Perhaps you should try some spelling variations:
"improving rural performance series." » "improving rural performance studies.", "improving rural performance size.", "improving euract performance series.", "improving larval performance series.", "improving pupil performance series."
"improving audit performance series." » "improving audit performance studies.", "improving audit performance size.", "improving budget performance series.", "improving credit performance series.", "improving student performance series.", "improving air 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 series.") or ("improving audit performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving rural performance series.") OR ("improving audit performance series.")).
• Removing quotes may allow a broader search: (( improving rural performance series. ) or ( improving audit performance series. )).
• Adding a wildcard symbol may retrieve word variants: (("improving rural performance series.") or ("improving audit performance series."))*.