Perhaps you should try some spelling variations:
"improving public performance series." » "improving music performance series.", "improving policy performance series.", "improving public performance studies.", "improving public performance size."
"improving based performance review." » "improving based performance risk.", "improving based performance evidence.", "improving board performance review.", "improving fund performance review.", "improving good performance review.", "improving basic performance review.", "improving care performance review.", "improving asset performance review."

Try widening your search to All Fields.

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