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 can performance evidence." » "improving chain performance evidence.", "improving loan performance evidence.", "improving 2 performance evidence.", "improving care performance evidence.", "improving a performance evidence.", "improving co 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 can performance evidence."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving human performance series.") OR ("improving can performance evidence.")).
• Removing quotes may allow a broader search: (( improving human performance series. ) or ( improving can performance evidence. )).
• Adding a wildcard symbol may retrieve word variants: (("improving human performance series.") or ("improving can performance evidence."))*.