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 targets." » "improving euract performance targets.", "improving larval performance targets.", "improving pupil performance targets."

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