Perhaps you should try some spelling variations:
"improving social performance studies." » "improving social performance audits.", "improving social performance audit.", "improving social performance standards.", "improving school performance studies.", "improving fiscal performance studies.", "improving financial performance studies."
"improving human performance series." » "improving human performance size.", "improving loan performance series.", "improving thermal performance series.", "improving chain 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 human performance series.") or ("improving social performance studies."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving human performance series.") OR ("improving social performance studies.")).
• Removing quotes may allow a broader search: (( improving human performance series. ) or ( improving social performance studies. )).
• Adding a wildcard symbol may retrieve word variants: (("improving human performance series.") or ("improving social performance studies."))*.