Perhaps you should try some spelling variations:
"improving human performance metrics." » "improving human performance measures.", "improving loan performance metrics.", "improving thermal performance metrics.", "improving chain performance metrics."
"improving animal performance series." » "improving animal performance studies.", "improving animal performance size.", "improving annual performance series.", "improving thermal performance series.", "improving fiscal performance series.", "improving initial performance series.", "improving optimal performance series.", "improving criminal performance series."

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