Perhaps you should try some spelling variations:
"improving thermal performance review." » "improving thermal performance risk.", "improving thermal performance evidence.", "improving external performance review.", "improving animal performance review.", "improving erm performance review."
"improving rural performance series." » "improving rural performance studies.", "improving rural performance size.", "improving euract performance series.", "improving larval performance series.", "improving pupil 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 review.") or ("improving rural performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving thermal performance review.") OR ("improving rural performance series.")).
• Removing quotes may allow a broader search: (( improving thermal performance review. ) or ( improving rural performance series. )).
• Adding a wildcard symbol may retrieve word variants: (("improving thermal performance review.") or ("improving rural performance series."))*.