Perhaps you should try some spelling variations:
"improve based performance series." » "improve based performance studies.", "improve based performance size.", "improve board performance series.", "improve fund performance series.", "improve good performance series.", "improve basic performance series.", "improve bank performance series.", "improve aid performance series."
"improving past performance evidence." » "improving plant performance evidence.", "improving port performance evidence.", "improving transit performance evidence.", "improving fast performance evidence.", "improving post performance evidence."

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