Perhaps you should try some spelling variations:
"improving outdoor performance series." » "improving outdoor performances series.", "improving outcomes performance series.", "improving poor performance series.", "improving outdoor performance studies.", "improving outdoor performance size.", "improving indoor performance series.", "improving our performance series."
"improving rural performance review." » "improving rural performance risk.", "improving rural performance evidence.", "improving euract performance review.", "improving larval performance review.", "improving pupil performance review."

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 review.") OR ("improving outdoor performance series."))~.
• Removing quotes may allow a broader search: (( improving rural performance review. ) or ( improving outdoor performance series. ))~.
• Adding a wildcard symbol may retrieve word variants: (("improving rural performance review.") or ("improving outdoor performance series."))*.