Perhaps you should try some spelling variations:
"improving good performance series." » "improving good performance studies.", "improving good performance size.", "improving fund performance series.", "improving court performance series.", "improving 2 performance series.", "improving food performance series.", "improving blood performance series.", "improve good performance series."
"improve country performance review." » "improve country performance risk.", "improve country performance evidence.", "improve community performance review.", "improve contract performance review.", "improve contrast 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 good performance series.") or ("improve country performance review."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving good performance series.") OR ("improve country performance review.")).
• Removing quotes may allow a broader search: (( improving good performance series. ) or ( improve country performance review. )).
• Adding a wildcard symbol may retrieve word variants: (("improving good performance series.") or ("improve country performance review."))*.