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

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