Perhaps you should try some spelling variations:
"improving basic performance series." » "improving basic performance studies.", "improving basic performance size.", "improving music performance series.", "improving baseline performance series.", "improving seismic performance series.", "improving air performance series.", "improve basic performance series."
"improving based performance evidence." » "improving board performance evidence.", "improving fund performance evidence.", "improving good performance evidence.", "improving care performance evidence.", "improving asset performance evidence.", "improving beef 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: (("improving basic performance series.") or ("improving based performance evidence."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving basic performance series.") OR ("improving based performance evidence.")).
• Removing quotes may allow a broader search: (( improving basic performance series. ) or ( improving based performance evidence. )).
• Adding a wildcard symbol may retrieve word variants: (("improving basic performance series.") or ("improving based performance evidence."))*.