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 brain performance evidence." » "improving chain performance evidence.", "improving loan performance evidence.", "improving can performance evidence.", "improving rail performance evidence.", "improving air performance evidence.", "improving basic performance evidence."

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