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