Perhaps you should try some spelling variations:
"improving human performance series." » "improving human performance studies.", "improving human performance size.", "improving loan performance series.", "improving thermal performance series.", "improving chain performance series."
"improving land performance review." » "improving land performance risk.", "improving land performance evidence.", "improving plant performance review.", "improving fund performance review.", "improving und performance review."

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

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