Perhaps you should try some spelling variations:
"improving maternal performance metrics." » "improving materials performance metrics.", "improving external performance metrics.", "improving national performance metrics.", "improving maternal performance measures.", "improve maternal performance metrics.", "improving water performance metrics."
"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.

• Performing a fuzzy search may retrieve terms with similar spellings: (("improving rural performance review.") or ("improving maternal performance metrics."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving rural performance review.") OR ("improving maternal performance metrics.")).
• Removing quotes may allow a broader search: (( improving rural performance review. ) or ( improving maternal performance metrics. )).
• Adding a wildcard symbol may retrieve word variants: (("improving rural performance review.") or ("improving maternal performance metrics."))*.