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

You may be able to get more results by adjusting your search query.

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