Perhaps you should try some spelling variations:
"improving maternal performance reviews." » "improving materials performance reviews.", "improving external performance reviews.", "improving national performance reviews.", "improving maternal performance review.", "improving maternal performance reports.", "improving maternal performance risks.", "improve maternal performance reviews.", "improving water performance reviews."
"improving thermal performance metrics." » "improving thermal performance measures.", "improving external performance metrics.", "improving animal performance metrics.", "improving erm 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 thermal performance metrics.") or ("improving maternal performance reviews."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving thermal performance metrics.") OR ("improving maternal performance reviews.")).
• Removing quotes may allow a broader search: (( improving thermal performance metrics. ) or ( improving maternal performance reviews. )).
• Adding a wildcard symbol may retrieve word variants: (("improving thermal performance metrics.") or ("improving maternal performance reviews."))*.