Perhaps you should try some spelling variations:
"improving country performance metrics." » "improving country performance measures.", "improving voluntary performance metrics.", "importing country performance metrics.", "improving community performance metrics."
"improving thermal performance series." » "improving thermal performance studies.", "improving thermal performance size.", "improving external performance series.", "improving animal performance series.", "improving erm performance series."

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