Perhaps you should try some spelling variations:
"improving maternal performance series." » "improving national performance series.", "improving lanterns performance series.", "improving water performance series.", "improve maternal performance series.", "improving maternal performance reviews.", "improving maternal performance review.", "improving maternal performance targets."
"improving thermal performance metrics." » "improving thermal performance contracts.", "improving thermal performance measures.", "improving thermal performance contract.", "improving rural performance metrics.", "improving human performance metrics.", "improving mental performance metrics."

Try widening your search to All Fields.

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