Perhaps you should try some spelling variations:
"improving music performance series." » "improving music performance studies.", "improving music performance size.", "improving public performance series.", "improving using performance series.", "improving seismic performance series.", "improving basic performance series.", "improvised music performance series.", "improving civic performance series."
"improving good performance evidence." » "improving fund performance evidence.", "improving court performance evidence.", "improving 2 performance evidence.", "improving food performance evidence.", "improving blood performance evidence.", "improve good performance evidence."

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (("improving music performance series.") or ("improving good performance evidence."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving music performance series.") OR ("improving good performance evidence.")).
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