Perhaps you should try some spelling variations:
"improving mental performance metrics." » "improving general performance metrics.", "improving senegal performance metrics.", "improving annual performance metrics.", "improving maternal performance metrics.", "improving fiscal performance metrics.", "improving gender performance metrics."
"improving rural performance measures." » "improving euract performance measures.", "improving larval performance measures.", "improving pupil performance measures."

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