Perhaps you should try some spelling variations:
"improving criminal performance series." » "improving critical performances series.", "improving regional performance series.", "improving animal performance series.", "improving critical performance series.", "improving civil performance series.", "improving criminal performance studies.", "improving criminal performance size."
"improving thermal performance review." » "improving thermal performance risk.", "improving thermal performance evidence.", "improving external performance review.", "improving animal performance review.", "improving erm performance review."

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 criminal performance series.") OR ("improving thermal performance review."))~.
• Removing quotes may allow a broader search: (( improving criminal performance series. ) or ( improving thermal performance review. ))~.
• Adding a wildcard symbol may retrieve word variants: (("improving criminal performance series.") or ("improving thermal performance review."))*.