Perhaps you should try some spelling variations:
"improving maternal performance metrics." » "improving national performance metrics.", "improving thermal performance metrics.", "improving lanterns performance metrics.", "improving maternal performance contracts.", "improving maternal performance measures.", "improving maternal performance contract.", "improve maternal performance metrics.", "improving water performance metrics."
"improving human performance reviews." » "improving human performance review.", "improving human performance reports.", "improving human performance risks.", "improving loan performance reviews.", "improving thermal performance reviews.", "improving company performance reviews.", "improving urban performance reviews.", "improving rural 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 human performance reviews."))~.
• Removing quotes may allow a broader search: (( improving maternal performance metrics. ) or ( improving human performance reviews. ))~.
• Adding a wildcard symbol may retrieve word variants: (("improving maternal performance metrics.") or ("improving human performance reviews."))*.