Perhaps you should try some spelling variations:
"improving neural performance series." » "improving neural performance studies.", "improving neural performance size.", "improving federal performance series.", "improving general performance series.", "improving annual performance series.", "improving natural performance series.", "improving rural performance series.", "improving central performance series."
"improving caring performance based." » "improving caching performance based.", "improving sharing performance based.", "improving coding performance based.", "improving learning performance based.", "improving reading performance based.", "improving imaging performance based."

Try widening your search to All Fields.

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