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 human performance risk." » "improving loan performance risk.", "improving thermal performance risk.", "improving chain performance risk.", "improving human performance 2019."

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

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