Perhaps you should try some spelling variations:
"improving co performance review." » "improving co performance risk.", "improving co performance evidence.", "improving ceo performance review.", "improving do performance review.", "improving core performance review.", "improving eco performance review.", "improving crop performance review.", "improving ict performance review."
"improving plant performance series." » "improving plant performance studies.", "improving plant performance size.", "improving port performance series.", "improving court performance series.", "improving land performance series.", "improving place performance series.", "improved plant performance series."

You may be able to get more results by adjusting your search query.

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