Perhaps you should try some spelling variations:
"improving can performance series." » "improving can performance studies.", "improving can performance size.", "improving chain performance series.", "improving loan performance series.", "improving human performance series.", "improving care performance series.", "improving a performance series.", "improving co performance series."
"improving job performance series." » "improving job performance studies.", "improving job performance size.", "improving court performance series.", "improving co performance series.", "improving food performance series.", "improving crop performance series."

Try widening your search to All Fields.

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