Perhaps you should try some spelling variations:
"improving country performance metrics." » "improving country performance measures.", "improving voluntary performance metrics.", "importing country performance metrics.", "improving community performance metrics."
"improving high performance series." » "improving high performance studies.", "improving high performance size.", "improving higher performance series.", "improving hiv performance series.", "improving birth performance series."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("improving country performance metrics.") or ("improving high performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving country performance metrics.") OR ("improving high performance series."))*.
• Removing quotes may allow a broader search: (( improving country performance metrics. ) or ( improving high performance series. ))*.