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 human performance series."
"improving pupil performance series." » "improving pupil performance studies.", "improving pupil performance size.", "improving social performance series.", "improving model performance series.", "improving judicial performance series.", "improving public performance series.", "improving civil performance series.", "improving audit performance series."

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 pupil performance series."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"improving rural performance series.\") OR (\"improving pupil performance series.\"))".
• Removing quotes may allow a broader search: (( improving rural performance series. ) OR ( improving pupil performance series. )).
• Adding a wildcard symbol may retrieve word variants: (("improving rural performance series.") OR ("improving pupil performance series."))*.