Perhaps you should try some spelling variations:
"improve using performance review." » "improve using performance risk.", "improve using performance evidence.", "improve business performance review.", "improve building performance review.", "improve savings performance review.", "improve housing performance review.", "improved housing performance review.", "improve testing performance review."
"improving past performance series." » "improving past performance studies.", "improving past performance size.", "improving plant performance series.", "improving port performance series.", "improving transit performance series.", "improving fast performance series.", "improving post performance series."

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: (("improve using performance review.") or ("improving past performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improve using performance review.") OR ("improving past performance series.")).
• Removing quotes may allow a broader search: (( improve using performance review. ) or ( improving past performance series. )).
• Adding a wildcard symbol may retrieve word variants: (("improve using performance review.") or ("improving past performance series."))*.