Perhaps you should try some spelling variations:
"improving voluntary performance review." » "improving country performance review.", "improving entry performance review.", "improving industry performance review.", "improving voluntary performance risk.", "improving voluntary performance evidence."
"improving past performance metrics." » "improving past performance measures.", "improving plant performance metrics.", "improving port performance metrics.", "improving transit performance metrics.", "improving fast performance metrics.", "improving post performance metrics."

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (("improving past performance metrics.") or ("improving voluntary performance review."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving past performance metrics.") OR ("improving voluntary performance review.")).
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• Adding a wildcard symbol may retrieve word variants: (("improving past performance metrics.") or ("improving voluntary performance review."))*.