Perhaps you should try some spelling variations:
"improving thermal performance series." » "improving thermal performance metrics.", "improving thermal performance reviews.", "improving thermal performance targets.", "improving maternal performance series.", "improving rural performance series.", "improving human performance series."
"improving export performance review." » "improving export performance risk.", "improving export performance evidence.", "improving labor performance review.", "emerging export performance review.", "improving upper performance review."

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