Perhaps you should try some spelling variations:
"improving pupil performance contract." » "improving pupil performance contracts.", "improving social performance contract.", "improving model performance contract.", "improving judicial performance contract.", "improving public performance contract.", "improving civil performance contract.", "improving audit performance contract."
"improving rural performance series." » "improving rural performance studies.", "improving rural performance size.", "improving euract performance series.", "improving larval performance series.", "improving human performance series."

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

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