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