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 social performance reviews." » "improving social performance review.", "improving social performance reports.", "improving social performance risks.", "improving school performance reviews.", "improving fiscal performance reviews.", "improving financial performance reviews."

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

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